iiSiiPiüiilii [i ;'i 2 i 1 DANSK BOTANISK ARKIV UDGIVET AF DANSK BOTANISK FORENING 3. BIND KØBENHAVN H. HAGERUPS BOGHANDEL 1915—1920 Nr. 1 a, S. 1—80, udkom Januar 1915 Nr. 1 b, S. 81—144, — Oktober 1916 Nr. 1 c, S. 145—240, — Oktober 1917 Nr. 1 cl, S. 241—304, — November 1918 Nr. 1 e, S. 305—368, — November 1919 Nr. ir, S. 369—504, — Oktober 1920 l\ 'i. REDAKTION: L. Kolderup Rosenvinge BIANCO LUNOS BOGTRYKKERI INDHOLD Nr. 1. F. Borgesen: The marine Algæ of the Danish West Indies. Part 3. Rhodophyceæ. With Addenda to the Chlorophyceæ, Phæophyceæ and Rhodophyceæ. With 435 figures. Bd.3 • DANSK BOTANISK ARKIV • Nr. l UDGIVET AF DANSK BOTANISK FORENING The marine Algæ of the Danish West Indies. Part 3. RHODOPHYGEÆ. By F. Borgesen. INTRODUCTION A. lS was the case with the parts of "The marine Algæ of the Danish West Indies" pubhshed earher, this third part, containing the Rhodophyceæ, is based especially upon materials collected during my three stays at the islands. With regard to West Indian Red Algæ I have already published some papers on the subject, namely: Some new or little known West Indian Florideæ, I. (Botanisk Tids- skrift, 30. Bind, København 1909). Some new or little known West Indian Florideæ, II. (Botanisk Tids- skrift, 30. Bind, København 1910). For the sake of completeness I have included here the principal contents of these papers. The Red Algæ are common in the litoral region and also in the upper sublitoral, but they occur especially in deep water, and where I succeeded in dredging in such places I always had good results. Thus they occurred abundantly in the Sound between St, Thomas and St. Jan, Strong currents run here in the narrow channel and steadily renew the water. The depth varies from 10 to about 20 fathoms, seldom more. The bottom is suitable for dredging ; it consists of smaller and larger stones, pieces of corals etc. Upon these a very rich vegetation of algæ is present, mostly consisting of Red Algæ. Also north of St, Jan, in the narrow sound between this Island and Tortola, a flourishing algal vegetation is found, including especially many Red Algæ. Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1915). 1 2 Dansk Botanisk Arkiv, Bd. 3, Nr. 1. At St. Thomas I have dredged in the sea around Water Island. At a depth of about 10 fathoms and upon sandy, loose bottom a vegetation of Udotea and Halimeda was found, together with several Florideæ. At St. Croix the dredgings were mostly not successful on account of the coral reefs which almost entirely surround the island. Only in the sea near Buck Island have more successful dredgings been undertaken. I much regret that I have not succeeded in dredging in deeper water than about 20^ — 25 fathoms ; as pointed out in the intro- duction to the Chlorophyceæ section, my attempts at this were negative, the dredge being immediately lost in the rocky bottom. But it is not only in deep water that the Red Algæ occur; also in shallow water near the shore they are often found in great numbers. In connection with this may also be borne in mind the rich algal vegetation upon the roots of the mangroves and among which the red algæ are very prominent, i) With regard to the physiographical details, coral reefs, depths etc. and also to localities visited, reference should be made to the introduction to the section on the Chlorophyceæ ; in this part' moreover a chart is published showing the coral reefs, depths etc. in the sea surrounding the islands. ^) Compare my treatise : "The algal vegetation of the lagoons in the Danish West Indies" in "Biologiske Arbejder tilegnede Eng. Warming den 3. November 1911", p. 41. F. Børgesen: Rhodophyceæ of the Danish W. Indies. RHODOPHYCEÆ A. Protoflorideæ. I. Bangiales. Fam. 1. Bangiacece, Subfam. 1. Goniotrichieæ. Asterocytis Gobi. 1. Asterocytis ramosa (Thwaites) Gobi. Gobi, C, in Arbeiten St. Petersb. Naturf. Ges., Bd. X, 1877, p. 85. Schmitz, Fr., in Nuova Notarisia, 1894, p. 717; id. in Engler u. Prantl, Nat. Pflanzenfam., I. Part, 2. Abt., p. 314. Wille, N., Algolog. Notiz., 1— IV (Nyt Magazin f. Naturv., Bd. 38, 1900, p. 7, tab. 1, figs. 8—14). Rosen- vinge, L. Kolderup, The marine Algæ of Denmark, 1909, p. 77. Hormospora ramosa Thwaites in Harvey, Phycologia Brit., pi. 213. Goniotrichum ramosum Hauclc, Meeresalg., p. 517. Batters, Mar. Alg. Berwick, p. 13; Lakowitz, Algenfl. Danziger Bucht, 1907, p. 79. Growing upon specimens of Liagora elongata I have several times found a small alga which undoubtedly belongs to this genus and as these specimens seem to differ in no essential way from A. ramosa I have referred them to it. The specimens found were often rather large and repeatedly branched (Fig. la); in some specimens the vegetative cells were nearly globular or subquadrate, about as long as broad, in others the cells were oblong or ellipsoidal (Fig. 1 h). This plant has been recently examined in detail by Wille (1900, I. c.) and by Rosenvinge (1909, 1. c). Wille describes the setting free of the spores which is as pointed out by Rosenvinge in accordance with the earlier description of Schmitz. Wille describes furthermore some few cells with membranes which he supposes to be akinetes. Rosenvinge has now stated that the supposed akinetes of Wille are really such. He was fortunate enough to find filaments in which nearly all the cells were trans- formed to akinetes. Dansk Botanisk Arkiv, Bd. 3. Nr. 1. In my material also I have found several times filaments in which the most part of the cells were transformed to akinetes (Fig. 1 d). These cells had each a very thick wall (about 2// thick) of a firm consistency, while on the other hand the common membrane in the whole filament is thin agreeing with the des- cription of ROSENVINGE. The akinetes escape through a hole in the membrane of the filament (comp. fig. 1 d). They have very dense granular contents and are often oblong, sometimes also globular or ellipsoidal ; their diameter reaches a length of about 14//. The filaments reach a thickness of about 16 — 21 fi, while the vegetative cells are about 6 — 7 fji. In one case a specimen was found in which the main filament was about 25// and the diameter of the cells about 10 ju while the branches only reached the thickness mentioned above. Rosenvinge also mentions that he has found a single specimen of a similar thickness. The chromatophore is, as well known, starlike (Fig. 1 c). Having only examined specimens preserved in spirit I cannot say anything as to the colour of the plant. As several authors have stated that they have found Asterocytis ramosa in brackish water (comp. Rosenvinge, 1. c. p. 78) I may add that the plant in the West Indies was found in quite salt water. Found upon Liagora elongata at Long Point, St. Croix. Geogr. Distrib. Atlantic coast of Europe, Mediterranean Sea, North America. Asterocytis ramosa (Twaites) Gobi, a, part of a plant, b, summit of a filament with lon- ger cells, c, cells with chromatopho- re. d, part of a fila- ment with akinetes. (aand6,aboutl25:l, candc^, about 200 :1). Goniotrichum Kütz. 1. Goniotrichum elegans (Chauv.) Le Jolis. Le Jolis, Alg. mar. Cherb., p. 103. Berthold, Bangiaceæ, p. 26. Hauck, Meeresalgen, p. 518. Ro- senvinge, Marine Alg. of Denmark, part I, p. 75. Bangia elegans Chauvin, Alg. Norm. no. 159 ; Mém. Soc. Linn. Norm., t. G, 1838 (not seen), id., Recherches . . d'Algues, Caen. 1842, p. 33. Harvey, Phyc. Brit., pi. 246. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 5 Bangia Alsidii Zanard., Bibl. Ital., t. 96, 1889 (not seen); id., Synop- sis Alg. mar. Adriat. (Memorie d. r. Accademia d. Scienze di Torino, Serie II, Tomo IV, 1842, p. 217, tab. VI, fig. 7). Goniotrichum Alsidii (Zanard.) Howe, The marine Algæ of Peru (Me- moirs of the Torrey Botanical Club, vol. XV, 1914, p. 15'). The specimens found reached a length of about 1mm.; at their base they were about 25 — 3b ju thick, at the summit only about Ibjui. They are fixed to the substratum by means of a small disc formed by the basal cell (Fig. 2 c). Fig. 2. Goniotrichum elegans (Chauv.) Le Jolis. a and b, parts of the thallus showing ramification, c, base of a plant. d, summit of plant with longitudinally divided cells. (About 150 : 1). The fdaments (Fig. 2 a and b) consist for the most part of a single row of cells and in some specimens these were almost the only ones which occurred, but several specimens had filaments which more or less consisted of 2 — 3 or even 4 cells in transverse section. The cells in these filaments are irregularly arranged, ') The reason I do not follow Dr. Howe in using Zanardini's name for this species is because it seems impossible judging from Zanardini's description and figure to say quite certainly which species of Goniotri- chum we have to do with. 6 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. occurring in irregular rows. These specimens certainly approach the form described by Berthold in his "Bangiaceæ" p. 26 as Goniotrichum dichotomum and found in the Gulf of Naples, but he found up to eight cells in a cross section of the thallus while, as mentioned above, I found 2—4 only. Hauck refers Berthold's plant to Goniotrichum Cornu Cervi (Reinsch) Hauck i) but in this species there are many more cells together in the filaments at the same level. My plant evidently comes very near to the form from the coast of Peru mentioned by Howe 1. c. In the specimens from the Danish waters which are figured and described by Rosenvinge we find now and then more than a single cell at the same level. According to Rosenvinge's statement this was caused in the specimens examined by him not by longitudinal walls but by displacement of the cells. In addition to this way of obtaining several cells in the filaments the multiplication of the cells in my plants is certainly also due to longitudinal division of the cells (comp. fig. 2 d). The cells contain a starlike chromatophore with a central pyrenoid. In the filaments consisting of a single row of cells these are mostly short, often only a fourth part of their diameter; the most common is that about half their length, more rarely they are about as long as broad. The diameter of the cells is about 12^^. In the filaments on the other hand consisting of several cells these are most often about as long as broad and by mutual pressure of irregular polygonal shape. The ramification is described in detail by Rosenvinge; it reminds one as is well-known of the so-named false branching of the Scytonemataceæ. Concerning the reproduction Rosenvinge has not made any observation and I have not succeeded in finding anything in my material. The plant is found partly upon other algæ partly upon different substrata e. g. old pieces of tree etc. It seems to be a common plant at the islands. St. Thomas: French Wharf. St. Jan: Near America Hill. St. Croix: Christianssted, Lt. Princess, Frederikssted and other places. Geogr. Distrib. Europe, Mediterranean Sea, Maroc, Peru. 1) Hauck, F., Meeresalgen, p. 17. This species was first described by Reinsch in "Contributiones", vol. I, 1875, p. 40, pi. XV and here called Stylonema Cornu Cervi. I F. Børgesen : Rhodophyceæ of the Danish W. Indies. 7 Subfam. 2. Erythrotrichieæ. Erythrotrichia Areschoug. 1. Erythrotrichia cariiea (Dillw.) J. Ag. J. Agardh, Till Algernes Systematik, VI, Ulvaceæ (Lunds Univ. Års- skrift, t. XIX, 1883, p. 15. Rosenvinge, Mar. Algæ of Denmark, part I, 1909, p. 67. Conferva carnea Dillwyn, British Conferv., 1809, pi. 84. Conferva ceramicola Lyngb., Hydrophytol. 1819, p. 144, pi. 48 D. Bangia ceramicola Chauvin, Recherches sur l'org. . . . d'Algues, Gåen 1842, pag. 29—30; Harvey, Phycol. Brit., pi. 317. Erythrotrichia ceramicola Aresch., Phyc. Scandinav. 1850, p. 210; Le JoLis, Alg. mar. Cherb., 1880, p. 103, pi. 3, fig. 1 — 2; Berthold, Bangia- ceæ, 1882, p. 25. The plant is, as mentioned and figured by Rosenvinge, fastened to the substratum by the basal cell which forms an irre- gularly lobed disc often with ramified rhizines radiating from it. The length of the vegetative cells is rather variable ; most often the length is shorter than the breadth, but cells longer than broad occur. The cells contain a starlike chromatophore with a large pyrenoid and a small nucleus not always easy to find as it is often, as pointed out by Rosenvinge, hidden behind the chromatophore. The reproductive cells are commonly somewhat longer than the breadth, the sporangium was of about the same size as the sister cell or somewhat smaller. It has been gathered in the months December — March and was in fruit it that time. It occurs epiphytically upon larger algæ, e. g. Sargassum, Acanthophora etc. and seems to be rather common. Geogr. Distrib. Atlantic coast of Europe and North America, Medi- terranean Sea, Maroc, West coast of North America etc. Erythrocladia Eosenv. 1. Erythrocladia subintegra Rosenv. Rosenvinge, L. Kolderup, The marine Algæ of Denmark, Part I, København 1909, p. 73. This plant was found epiphytic (Fig. 3 d) ^) upon specimens of Chætomorpha and Cladophora upon which it forms small roundish ^) In contradiction to the statement of Rosenvinge, Howe (in "The marine Algæ of Peru", p. 82) is of the opinion that it is ordinarily immersed in the wall of the host and that it is "endophytic rather than epiphytic". 8 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. or more irregularly shaped discs up to 300^ in diameter or even more. The young specimens have a nearly circular or somewhat undulate continuous margin (Fig. 3, a and b), in older specimens it is more irregular and the extremeties of the filaments become Fig. 3. Erythrocladia subintegra Rosenv. a, b, young plants seen from above, c, older plants with more irregular margin, d, transverse section of the thallus. (About 700:1). more or less free (Fig. 3 c). It has marginal groxN^h and, as pointed out by Rosenvinge, the cells are dichotomously divided but the bifurcation is most often not quite equal, the one cell being larger than the other. Near the margin the cells are often linear-oblong or forked, in the middle shorter, oblong, or of more irregular shape. The diameter of the cells is mostly 3 — 4 fi but it is very variable and so also the length which often reaches up to 16« or more. The chromatophore was not clearly visible but it seems to be Fig. 4. Erythrocladia subintegra parietal with a pyrenoid in the middle Rosenv. Part of a plant seen of the cell. from above. In some of the rpii • /-c^- a\ cells sporangia are cut off. The sporangia (Fig. 4) are as (About 700 : 1). said by Rosenvinge cut off in the ends of the vegetative cells through a somewhat curved wall ; they are of variable shape and size, mostly roundish orbicular and about 3 — 4/^ broad. In referring this plant to the genus Erythrocladia I confess that it is not without doubt. According to Rosenvinge 1. c. p. 72 F. Børgesen: Rhodophyceæ of the Danish W. Indies. 9 the thallus of this genus "consists of mutually separate filaments which only at a later stage are partly confluent" ; this corresponds with Erijthrocladia irregularis but how far it does with Erythro- cladia subintegra seems more doubtful. Rosenvinge ^has not found young specimens of his plant but such occurred often in my material and as pointed out above the young specimens have a continuous margin with no free ends; in the older specimens, on the other hand, with more irregular margin free ends are present. These older specimens agree very well with the figures 13 and 14 of Rosenvinge and also with specimens in a preparation which he has most kindly allowed me to examine. Dr. Rosen- viNGE discusses the possibility as to how far this species ought to be referred to the genus Erythropeltis Schmitz i) but as pointed out by him such a comparison is difficult to undertake as Ery- thropeltis is imperfectly known. In my opinion this genus of Schmitz is very problematic as is also pointed out by Howe ^): "Schmitz, in proposing the new generic name Erythropeltis for Erythrotrichia discigera Berthold (which he cites as the monotype of his new genus without any pro parte reservations), omits any reference to the erect filaments described and figured by Ber- thold". Erect filaments have not been found neither in Rosen- vinge's nor in my plant. On account of these facts it seems to me not impossible that this species ougth to be regarded as a representative for a new genus. Yet I want to point out that my plant seems to show much hkeness to the discs found in the newly described Erythrotrichia polymorpha Howe 3) and especially to those forms found upon Chætomorpha cartilaginea and Cladophora fascicularis in which the erect filaments often are wanting. If we compare my figures (Fig. 3 a and b) with e. g. figs. 5, 7 and 9 of Howe it cannot be denied that the similarity is striking, But the cells and sporangia are larger in Howe's plant, the disc is distromatic in the middle and erect filaments are also present. St. Thomas: In the Harbour, St. Croix: Northside Estate. Geogr. Distrib. Danish waters. Most probably widely spread. ^) In Engler & Prantl, "Nat. Pflanzenfam." I, Abt. 2, p. 313, 1896. ^) Howe, M. A., 1. c., p. 80. ') Howe, M. A., 1. c, p. 77. 10 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Subfani. 3. Bangieæ. Bangiopsis Scliinitz. 1. Bangiopsis siibsimplex (Mont.) Schmitz. Schmitz in Engler und Prantl, Natürl. Pflanzenfam., 1. Teil, 2. Abt., p. 314. Compsopogon subsimplex Montagne in Annales scienc. nat., Bot., III« sér., t. 14, 1850, p. 299. When young the plant is filamentous composed of a single row of cells. These in the young filaments are disc-shaped (Fig. 5 c), their length being much shorter than the breadth, often only a fourth in the newly divided cells. They are divided by horizontal walls and all cells are capable of division. The diameter of the fila- ments is about 35 jj.. The base of the plant consists of an enlarge- ment of the lowermost end of the basal cell, forming in this way a small disc by means of which the plant is faste- ned to the substratum (Fig. 5 h). I have not seen any rhizoids grow- ing out from the lower- most cells as is the case in Bangia. In the somewhat older filaments the cells now and then begin to be divided also by longitudinal or more or less oblique walls. This division of the cells is rather irregular; in some plants nearly the whole filaments are divided, in other we find parts of the filaments divided into many Fig. 5. Bangiopsis subsimplex (Mont.) Schmitz. a, part of a filament which begin to be rami- fied, b, part of a ramified thallus. c, filament composed of a single row of cells showing cell-division, in the upper end one cell divided by an obHque wall, d, e, f, g, transverse sec- tions of filaments consisting of a single to many cells, h, base of a plant, (a and b about 150 : 1, c—h, 200 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 11 cells and between these there are thinner parts still consisting of a single row of cells (Fig. 5 a). Figs. 5 d, e, /, g show transverse sections of filaments in differ- ent stages of development; fig. 5 c? is of a filament still consisting of a single row of cells, in fig. 5 e we find two cells and in fig. 5 / and g several. As the figures show the cells lie scattered without order in the whole filament. In this my plant differs essentially from the description of Schmitz (1. c.) where the thallus is said to be : "der ganzen Länge nach röhrig hohl, mit gallertgefülltem Hohlräume". Now and then especially from the thicker parts of the fila- ments branches grow out; these are commonly short, proliferation- hke, consisting of a single row of cells (Fig. 5 b, Fig. 6) ; only rarely I have found them longer and more like the main filaments. Each cell contains a starlike red-violet chromatophore in the middle of which a large pyrenoid is present (Fig. 6). In some filaments , all or nearly all cells were emptied, the few remaining cells were nearly spherical and with a granulated contents. I take these cells for the gonidia. I have not succeeded Fig. 6. Bangiopsis subsimplex (Mont.) in findincT othor kind of organs Schmitz. Part of a thallus showing m imdmg otner Kma oi organs ^^^^^ ^.^^^ chromatophores and pyre- of propagation. noids. (About 250 : 1). While my plant seems to agree quite well with the description of Montagne it differs as pointed out above from that of Schmitz's by its solid thallus. Montagne referred the plant to the genus Compsopogon, while Schmitz created for it the genus Bangiopsis. It comes surely near to Bangia but differs essentially from this genus by the want of rhizines at the base and by the common presence of prohferations and especially by the rather irregular cell-division, the cells in Bangia being divided by radial walls and these as a result are generally wedge-shaped. The plant has been found only once growing upon a buoy in the harbour of Christianssted, St. Croix. Geogr. Distrib. Guiana. mm ' 12 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. B. Florideæ. I. Nemalionales. Fam. 1. Helminthocladiaceæ. Subfam. 1. Chantransieæ. Acrochætium Nagl. After an exhaustive enquiry as to the correct generic name for the plants hitherto usually grouped under Chantransia I have come to the conclusion, in agreement with the opinion, amongst others, of J. Agardh^), Batters 2) and quite recently M. A. Howe 3) that we must adopt Nägeli's name Acrochætium^). I will shortly give my reasons for this. The genus Chantransia was originally created by De Candolle ^) but, as pointed out by Thuret^), his genus includes forms of genera as different as Lemanea, Batrachospermum, Cladophora and Oedogonium and has therefore nothing to do with the genus Chantransia as now understood. It was first Fries') who in 1825 reorganized it more pre- cisely giving as types of the genus the two freshwater forms Conferva Hermanni and Conferva chalybæa Roth. But before this Bory^) had already referred these plants to his new genus Aiidouinella. From this fact alone the genus Chantransia Fries ought to be regarded as a synonym when the priority is strictly followed. But the position of this genus became yet more untenable when it was discovered by Sirodot^) ^) Agardh, J., Analecta Algologica, Lundæ 1892, p. 45. 2) Batters, E. A. L., A Catalogue of the British marine Algæ (Journ. of Bot., Supplem. 1902, p. 58). 3) Howe, M. A., The Algæ of Peru (Memoirs of the Torrey Bot. Club, vol. XV, New York 1914, p. 63). *) Nag ELI, Beiträge zur Morphologie und Systematik der Ceramiaceæ. (Sitzungsb. Königl. Bayer. Akademie der Wissensch., 1861, p. 402). 5) Lamarck et De Candolle, Flore Frangaise, t. II, 1805, p. 49. *) Thuret in Le Jolis, Liste des Algues de Cherbourg, 1864, p. 104. ') Fries, E., Systema orbis vegetabilis. Pars I, p. 338, Lundæ 1825. *) BoRY DE Saint-Vincent iu "Dictionnaire classique d'histoire natu- relle", t. 3, Paris 1823, p. 340. *) Sirodot, S., Les Batrachospermes. Paris 1884. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 13 and later by other investigators ^) that the freshwater Chantransiæ were only stages in development of Batrachospermum etc. ^). NÄGELI published his genus Acrochætium in 1861. It was based upon several marine forms known at that time. But in those days the freshwater Chantransia were considered as inde- pendent species, and these are, as is well known, so much like the marine ones that Nägeli ought to have referred the marine species to this genus as Thuret did some few years after. Had Nägeli done so, we should not perhaps have been obliged to give up this old generic name. Yet it should be born in mind that Schmitz 3) in 1889 reformed the genus Chantransia in a somewhat different sense to Thuret namely without including the freshwater Chantransia and in his sense therefore the genus equals Acrochætium. Owing to these facts it seems to me necessary to adopt Nägeli's name. In connection with this I will transcribe Bat- ters' conclusion as to this question. In his paper quoted above he writes p. 58: "Under these circumstances it seems to me that either the name Aiidouinella must be substituted for Chantransia as that genus was understood by Thuret (i. e. to include both freshwater forms, like C. chalybea and C. Hermanni, and marine, like C. corymbijera, C. ejflorescens, and C. microscopica), or, as seems preferable, to preserve the former name as that of a -doubtful genus of freshwater algæ, and to adopt Nägeli's genus Acrochætium for the reception of the well-understood marine forms". In 1904 BoRNET*) proposed to separate the species with sexual reproduction from those bearing only sporangia the first ones to be kept in the genus Chantransia the others to be refer- red to the genus Acrochætium. I quite agree with Rosenvinge that this distinction seems very artificial and in the following survey of the species found in the Danish West Indies I follow him and refer all the species to the same genus. 1) Comp. De Toni, Sylloge Alg., vol. IV, Sectio IV, p. 1863, the note. ^) Here I may call attention to the fact that Brand (in his paper: Über die Siisswasserf ormen von Chantransia (D. C.) Schmitz, einschliesslich Pseudochantransia Brand, "Hedwigia" vol. 49) has pointed out that besides the Chantransia-like forms of Batrachospermum etc. there are also some independent species of Chantransia and among these Ch. Her- manni. This certainly needs further investigation. *) Schmitz, Fr., Systematische Übersicht der bisher bekannten Gattungen der Florideen ("Flora", 1889). ■*) BoRNET, E., Deux Chantransia corymbifera Thuret. Acrochætium et Chantransia (Bull. Soc. bot. de France, T. 51, Paris 1904). 14 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. In this connection, however, I may remark that in nearly all the species mentioned below I have looked in vain for sexual organs ; only in a single species, Acroch. Sargassi, were they found. Neither did tetrasporangia occur in the West Indian species collected by me; on the other hand I have previously described a species Acrochætium {Chantransia) bisporum in which sporangia divided by a cross wall into two spores were common and in another species, Acrochætium occidentale, described below some few sporangia divided in the same way were met with. In the above-mentioned paper by Bornet the eminent phy- cologist has pointed out that the development and structure of the basal part of the thallus is of great systematic value in a genus consisting of such small plants and, as to the vegetative and reproductive parts of the thallus, often so very similar. In his excellent treatment of the Danish species Rosenvinge also has largely based his differentiation and classification of the species on the method of development of the basal portion. In the West Indian material likewise it has been evident that excellent characters may be found in the base of the thallus and I have succeeded in finding not only most of the types mentioned by Rosenvinge but also others coming near to some mentioned by Bornet. It has, however, not always been an easy matter to follow the development of the germinating spore. When several species grow together this is most often impossible ; upon the leaves of an old Sargassum vulgare was found at least six different species and here it was very difficult to clear up the structure of the basal part, and its development from the germinating spore was quite out of the question. Of one species mentioned below I have only succeded in finding a single specimen and have not been able with certainty to state the structure of the base; but as the plant had a very characteristic appearance I think it is entitled to a description. When speaking of the basal part I wish also to point out that there are many connecting links from the epiphytic to the endophytic species. In Acrochætium. crassipes the lowermost part is, when growing upon a plant of soft surface, often some- what immersed ; on the other hand when growing upon the spines of Centroceras it seems not immersed at all. Upon Avrainvillea nigricans was found an Acrochætium (A. Avrainvilleæ) whose base, composed of short creeping filaments, was fixed to filaments rather deeply sunk in the tissue of the host plant. The tissue of A. nigricans is very loose and open F. Børgesen: Rhodophyceæ of the Danish W. Indies. 15 and the erect filaments of the Acrochætium have not much difficulty in immerging from it. From this stage of endophytism, if such it ought be called, there is an even transition to those species (as Acrochætium occidentale and Aer. comptum) fixed to the assimilating filaments of Liagora. The space between the fila- ments of the species belonging to this genus is filled with mucilage and also with more or less of a chalk incrustation. The basal filaments of the above mentioned Acrochætium species creep epiphytically upon the filaments of the host plant, but they are on the other hand immersed in the mucilage. Quite immersed in this mucilage is Acrochætium Liagoræ. In other species again the endophytic filaments are able to penetrate more or less into the cellular tissue of the host plant. Here also graditions may be observed. In some species e. g. Acrochætium robustum, unipes and others only short endophytic processes are present. In Acrochætium hormorhizum the basal part is immersed in the thick wall of the host plant. Acrochætium repens has endophytic filaments creeping extensively in the tissue of the host plant sending up here and there erect free filaments. Further as pointed out by Kylin and later by Rosenvinge the shape of the chromatophore is of great systematic importance. Referring for details to Rosenvinge's description I will here only mention that by far the greatest number of the West Indian species have a parietal more or less lobed chromatophore with a lateral excentric pyrenoid protruding more or less into the lumen of the cell. In other species a stellate chromatophore with a central pyrenoid is found. The following classification of the species is based essentially upon the different development of the basal part, next upon the shape of the chromatophore and other characters. Key to the West Indian species of Acrochætium. A. Epiphytes. a. A single undivided basal cell. 1. With sex-organs, chromatophore parietal 1. A. Sargassi. 2. Without sex-organs, chromatophore stellate .... 2. A. crassipes. b. The germinating spore is divided into two cells . . . 3. A. pulchellum. c. Basal layer multicellular, composed of creeping fila- ments fusing more or less together. 16 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 1. Erect filaments about 5—6,« thick. a. Sporangia sessile or pedicellate, fusiform .... 4. A. netrocarpiim. ß. Sporangia sessile or pedicellate or several to- gether upon short branchlets, oblong-hnear . . 5. A. gracile. y. Branchlets mostly opposite with mostly several sporangia 6. A. globosum. 2. Erect filaments about 8 — 10 j« thick. a. Cells proportionally short, mostly barrel-shaped, hairs present 7. A. Sancti Thoniæ. ß. Cells cylindric, hairs wanting. aa. Sporangia seriate, mostly sessile, sometimes . . pedicellate 8. .4. seriatum. bb. Sporangia mostly placed 1 — 2 upon bran- chlets 9. A. flexuosum. B. The base of the plant partly endophytic. a. Germinating spore persistent at the base of the plant. a. Spore with a single endophytic, obovate or subclavate, descending process .... 10. A. iinipes. ß. Spore with a cuneate process and, sometimes, with short epiphytic horizontal branches 11. A. opetigenum. b. Epiphytic basal disc with endophytic process 12. A. robustiim. c. Epiphytic and endophytic filaments ... 13. ^. bisporiim. C. The whole base of the plant endophytic. a. The germinating spore persistent and easily recogniz- able. 1. The spore remains undivided 14. ,4, occidentale. 2. The germinating spore is divided into two cells . . 15. A. comptum. b The original spore not recognizable. 1. Base composed of more or less horizontal creeping filaments. a. The base immersed in the loose tissue of the host plant 16. A. Avrainvilleæ. ß. The base immersed in the thick wall of the host plant; endophytic filaments moniliform . . 17. A. hormorhiziim. y. The endophytic filaments immersed in the wall and between the cells of the host . . 18. A. Hypneæ. d. The endophytic filaments widely spread in the tissue of the host . : . 19. ^. repens. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 17 2. A multicellular vertical basal layer 20. A. phacelorhizum. D. The whole plant immersed in the host plant . 21. A. Liagoræ. In addition is described below A.ernothrix the base of which I have not succeeded in seeing clearly. 1. Acrochsetium Sargassi nov. spec. Thallus usque ad 700;/ altus. E cellula basali, discum par- vum formante, filum erectum, a basi ramosum, egreditur. Rami sparsi aut secundati aut oppositi, simplices aut ramosi, ad apicem versus attenuati, in pseudopila sæpe producti, ex cellu- lis in parte inferiori thalh 5,5// latis, 9—18;/ longis, in superiori parte 2—3// latis, 30-40/« longis composite Ghromatophorum parietale, pyrenoide laterali instructum. Sporangia sparsa aut pauca secundata, in ramulis sæpe bina præsentia, sessiha aut pedicellata, obovata, 10/« longa, 7// lata. Antheridia in ramulis opposita aut plus minus irregulariter aggregata, globularia, ca. 2// lata; carpogonia lageniformia, sessilia. This plant reaches a length of up to 600 — 700 //. The base (Figs. 7 and 8 a) consists of a flat disc (about 20// diameter) formed by the original spore and apparently in a similar way to that found in Acrochsetium {Chantransid) microscopicum Nægl. var. collopoda Rosenvinge, described and figured by Ro- SENViNGE in "Deuxieme Memoire sur les Algues mar. du Groen- land" (Meddelelser om Grønland, XX, p. 412). By means of this small disc the plant is fixed firmly to the host plant (old leaves of Sargassum vulgare). From this disc is given off a single filament which immedia- tely begins to branch (Fig. 7). The cells in the lowermost part of the filaments are short and have thick walls ; they are about 9// long and 5,5 /« broad, in vigorous plants up to 8// broad. Higher up the cells grow longer, up to about 18 /i, tapering at the same time, and the filaments end with long, thin nearly colour- less, hairlike prolongations which soon die away; in these the cells are only 2—3// broad while their length is about 30—40« or more. Rosenvinge also found such discoloured prolongations in several species and compared them with the hair-Hke organs in the Phæophyceæ. Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1915). 2 18 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The filaments are as a rule very stiff and straight and arise from the principal filaments, often serially, sometimes Fig. 7. Acrochastium Sargassi nov. spec. Habit of a plant with monosporangia and antheridia. (About 180 : 1). scattered, and now and then opposite (Fig. 7). The branches are similarly ramified and run out into long hair-like organs. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 19 The chromatophore is usually slightly developed (Figs. 9 and 10); it is parietal often with some long irregularly shaped pro- longations ; in some of the cells it often consists only of a small portion surrounding the pyrenoid and lying at the wall of the cell. The sporangia are found either at the base of the filaments upon their upper side some- times solitary, some- times two or three to- gether, or they may occur upon short bran- chlets given ofT from the principal filaments. They are mostly pedicellate but sessile ones also occur. The sporangia are oval-obovate (Fig. Sb, 9); their length is about 10//, their breadth about 7 /J.. This is the only West Indian species in which sexual organs were found. Specimens with antheridia were seen several times (Fig. 7). The antheridia occurred in pairs along both sides of the small fertile branch- lets (Fig. 10) but were now and then more irregularly arranged. For a long time I searched vainly for the carpogonia and finally I succeded in find- ing a specimen in which some few carpogonia undoubtedly were present. As Fig. 8 c shows Fig. 9. Acrochætium ^^qj are bottle-shaped having nearly the same ST'of tSe^thSlus form as in other species. No later stages of with sporangia. The carpogonia were found. emp'Stnd" tw This plant seems to come very near to one is growing out Acrochætium Dufourii Collins and I have been again, (about 600:1). .^ ^^^^^ ^^^j^^ ^^^ ^^^ ^j^^^ pj^^^ i^ ^^.^eed only a young state of my species. But after having examined the original material of Acroch. Dufourii, distributed in "Phyc. Bor.-Am.", No. 1594 I think it is not. 2* Fig. 8. Acrochætium Sargassi nov. spec. a, plant with sporangia, b, part of a filament with sporangia, c, part of a plant with carpo- ■ (a. about 100 : 1, b, 500 : 1, c, 400 : 1). gonia 20 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. A general difference must be pointed out in the fact that Acrochæt. Dufoiirii seems to be somewhat smaller in all parts of its thallus. The base in both plants appears to be very alike ; in both it is a somewhat flat, upwards convex, below nearly plane disc, formed by secretion of the basal cell; it is smaller in Acr. Dufourii than that found in my plant, but in one specimen it reached a diameter of about 14//. In Acr. Dufourii the erect filaments are about 4 — bfi broad, in my plant the filaments at their base are mostly 5 — 6 but specimens occur in which the filaments are S/u thick. But while, and this is the most essen- tial difference, the plant of Mr. Collins does not Fig. 10. Aero- taper towards its summit the filaments in my plant chætium Sar- taper very much and run out in thin nearly spec. Branch colourless hair-like prolongations. This is not men- with branch- tioned in the description of Collins and I have not antheridia been able to find any trace of this in the dried (About specimen in "Phycotheca". Besides, as is evident from the above description, my plant is much more branched and generally more developed (e. g. with sex organs) than Acr. Dufourii. This species occurred together with several other upon old leaves of Sargassum vulgare. St. Thomas: The Harbour. 2. Acrochætiiira crassipes Børgs. Børgesen, F., Some new or little known West Indian Florideæ, I. (Botanisk Tidsskrift, vol. 30, 1909, p. 1). var. ty pica nov. var. Børgesen, F., 1. c. My previous description of this plant was based upon few specimens only ; now by renewed efforts I have been fortunate enough to find it in other collections and this enables me to give some additions to my former description. The basal cell is subcylindric-barrelshaped with thick walls (Fig. 11 A, 5); in my former description I said that it was fastened to the surface of the host plant by means of. a rather thick layer of cementing substance and this is also the case where it is growing e. g. on the spines of Centroceras as shown in the fig. 11 .4 and B, but when found upon a more soft substratum e. g. upon Hypnea it sometimes, at any rate, is somewhat im- F. Borgesen: Rhodophyceæ of the Danish W. Indies. 21 Fig.ll. Acrochætium crassipes var. ty pica. A and B, two plants growing on Cen- troceras ; B, with a hair (300 : 1). C, piece of a branch mersed with the basal part in the wall of the host plant, in agreement with M. A. Howe's description of Acrochætium catenulatum'^). The basal cell bears as a rule one or two erect filaments which most often are more or less curved and decumbent and graduallly taper towards their summits, the basal cell being the thickest of all. Hairs seldom occur ; most of the plants are quite destitute of them. Where they with monosp'orangia (300 : 1) are present they are always to be found fj'^'p^^ ZTfliS^t at the tips of the filaments (Fig. 11 B). The chromatophore is stellate with a central pyrenoid. In most of the cells plenty of starch is present and the contents of the cells then have a quite homogenous appearance ; but when boiled and coloured e. g. by means of hæm- alun the stellate chromatophore is easily seen. var. longiseta nov. var. Upon specimens of Chætomorpha antennina from the harbour of St. Thomas and on Chætomorpha brachygona from Christianssted was found abundantly a small Acrochætium which shows so much likeness to Acrochætium crassipes that I have no doubt in referring it to this species from which it essentially differs by the usual presence of long hairs. The basal cell originating from the ger- minating spore is, as is the case in var. typica, the largest of the whole plant (Fig. 12), being 8 — 10 ^y. in diameter. It is fixed to the host plant by means of a ring of cementing sub- stance and, so far as I have been able to see, it is also often somewhat immersed in the wall of the host (Fig. 12, 13 e). From the basal cell arise a single or 2 — 3 suberect branches, the cells of which grow gradually thinner and at the same time longer towards Fig. 12. Acrochætium crassipes Børgs. var. longiseta nov. var. Plant with a single sporangium and hairs, in the cells the stel- late chromatophore with the central pyre- noid. (about 800 : 1). ^) M. A. Howe, The marine Algæ of Peru ("Memoirs of the Torrev Bo- tanical Club", vol. XV, 1914, p. 84). 22 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. the summit where their diameter is only about 4 — 5^ while the length of the cell is about 6 — 7^. The basal cell and the lower- most cells in the filaments are about as long as broad, often even a little shorter than broad. The principal filaments are as in the var. ty pica mostly very curved (Fig. 13 a, c) ; along the upward side of the filaments all the cells may bear sporangia, or in the more vigorous plants short branchlets ; more rarely some of the cells are provided with branches on the opposite side (Fig. 13 c). The cells contain a stellate chromatophore with a central pyrenoid (Fig. 12) quite in ac- cordance with that found in the var. ty pica. At the ends of the filaments long hyaline hairs occur (Figs. 12, 13), these are about 1 — 2fi thick and reach a length of about 50 ^. The sporangia are always monosporous ; they are oval- obovate, about 5 // broad and Y'lg.l'i. AcrochætiumcrassipesBøvg?,. 6 — Ifi long. They are mostly var Zonnsem nov. var. a, ^, c, habit ^ ^iui sometimes also pedi- 01 plants, a, a young plant, e, base ' ^ of a plant showing the immersed cellate or placed upon short nethermost part. \a, b c, about branchlets; now and then such 250 •.l\d,e, about 800 : 1). ' branchlets have two sporangia. The length of the larger specimens without hairs is about 60^. This species seems to be nearly related to Acrochætium {Chan- transia) moniliforme Rosenvinge and Acrochætium catenulatum Howe. From the first mentioned species it differs essentially in its smaller size in every respect, and by the proportionally larger basal cell. And Acrochætium catenulatum differs from our plant among other things by its larger size, want of hairs and ap- parently different chromatophore. This species has been found upon different host plants, namely, Hypnea, Centroceras, Bryopsis, Chætomorpha, Cladophora etc. It seems to be a common species especially in more sheltered places. Var. typica has been found at St. Thomas: in the Harbour and in Magens Bay, at St. Jan: in Cruz Bay and at St. Croix: near Christianssted. Var. longiseta. St. Thomas: in the Harbour and at Water Island; St. Croix: at Christianssted. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 23 3. Acrochætium pulchellum nov. spec. Thallus minutus, pulviriatus. Pars basalis e filis repentibus ramosis, in parte centrali sensim confluentibus, composita. Spora germinans in duas cellulas fere æquales di visa est, quarum utra- que filum ramosum repens procreat. Gellulæ in parte basali irreguläres, breves, 7—10/^ longæ et o—Qfi latæ. Ex his cellulis fila erecta brevia, 1—3 raro plures cellulas continentia, ca. 24 /i alta, egrediuntur ; cellulæ b—Qfx latæ, diametro IV2— 2-plo longiores, chromatophorum stellare pyrenoide centrali instructum continentes. Pili hyalini terminales, ca. 100 /i longi, 2—3 // lati, numerosi. Sporangia in filis erectis terminalia, raro in filamentis repentibus sessilia, ovata, 5 — 1 (x lata et 9—10// longa. Of the species described by Rosenvinge the present plant seems to come nearest to Acr. (Chr.) hiimile; in its mode of growth and the structure of the cells it also some- what resembles A. (C.) polyblastam Rosenv. but the erect filaments are not so large. In agreement with the above mentioned species the germinating spores are divided pig. 14. Acrochætium into two nearly equal cells (Fig. 14); in the ^",^^^4";Ent"37„\Xch young plants these cells are easily recogniz- the original spores, di- able, in the older they are most often not. vided into two cells, ' , „ . „, . are yet visible. From each of these cells a creepmg filament (About 600 : 1). is given off in opposite directions ; these filaments soon begin to branch, the branches in the middle fusing more or less together. By this method of growing a relatively large disc may be formed (Fig. 15). The cells are rather irre- gularly shaped with more or less sinuated walls, short, about 5—6// broad and 7 — 10// long. From the cells in the basal layer short erect filaments con- sisting of 1—3 seldom more cells arise. These filaments are terminated by long hyaline hairs or they may bear the sporangia (Fig. 15). Hairs also occur at the ends of the creeping filaments but are soon pushed aside. The hairs reach a length of 100// or more and 2—3// broad. They are, as mentioned above, hyaline; the young hairs are richly provided with protoplasm. The chromatophore is stellate with a central pyrenoid (Figs. 15 and 16). 24 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The erect filaments reach 24 /^ and occasionally higher ; their breadth is about 5 — 6 fx. Fig. 15. Acrochætium pulchellum nov. spec. Plant with monosporangia of which someones are emptied ; it creeps upon Chætomorpha. (About 700 : 1). The sporangia are mostly terminally placed upon the erect filaments ; more rarely sessile sporangia, placed immediately upon the cells of the basal filaments are found. The sporangia are ovate, about 5 — 7 fx broad and 9—10« long. This species has been found upon Chætomor- pha antennina in a very exposed place on rocky coast. St. Croix: Northside. 4. Acrochætium netro- carpiim nov. spec. Thallus cæspitosus ad 400/^ altus, e filis repentibus et fihs erectis numerosis compositus. Fila repentia ramosa, plus minus confluentia ex cellulis bre- vibus irregulariter formatis constructa. Fig. 16. Acrochætium pulchellum nov. spec Plant with hairs. (About 700 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 25 Fila erecta parce ramosa, 5 — 6/i lata, cellulis diametro triplo vel 4 plo longioribus, cylindricis, in parte superiori filorum cellulis tenuioribus, 3 — 4;/ latis, chromatophorum, ut videtur, parietale pyrenoide laterali munitum continentibus. Sporangia monospora, fusiformia apice truncato, sessilia aut pedicellata, sparsa aut unilateraliter seriata, 4—5^ lata, 10 — 11 /ji longa. This small species was found upon old leaves of Caiilerpa taxijolia. Only a single tuft was met with growing in com- pany with Acrochætium seriatum and other small epiphytes. It forms a dense low tuft up to about 400,« high. The basal part consists of creeping filaments (Fig. 11 d) fusing more or less together but, it would seem, easily separ- able. The cells in these filaments are Fig. 17. Acrochætium netro- rather short, often nearly isodiametric but ^^'PJ^"^ f'^ H^'^^ents' ^'tli much irregular in shape. From nearly all sporangia, d, base of the of these cells with the exception of those P A'a '-f' ^^^nÅ^^Kx^' ^' ^ 4o0 : 1 ; a, 600 : 1). near the margin erect filaments arise. These (Fig. 17 a) are multilaterally ramified but not much so, and taper somewhat towards the upper end (Fig. 17 c). They consist of cylindric cells about 18 — 20 /j. long; in the basal part these cells are about 5—6 ^ broad while those at the summit are only 3 — 4//. The shape of the chromatophore was not clearly visible, so far as I have been able to see it was parietal with a lateral pyrenoid ; the last mentioned was more visible in the sporangia (Fig. 18). The latter have a very characteristic shape (Figs. 17 b, 18) ; they are fusiform with a truncate p. g summit, about 4 — 5 fx broad and 10 — 11 /u long. Acrochætium They are mostly sessile but often also pedicellate. netrocarpum f^ey occur more or less in a series or may be more nov. spec. '' "^ FUamentwith scattered. sporangia. (About 800 : 1). This species has only been found once namely at Chri- stianssted, St. Croix. 26 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 5. Acrochætium gracile nov. spec. Thailus cæspitosus usque ad 1 mm. altus et ultra. Pars basalis e filis repentibus, epiphyticis, plus minus lateraliter confluentibus composita. Fila erecta, simplicia aut paucis ramulis Fig. 19. Acrochætium gracile nov. spec. a and b, erect filaments with sporangia, c, base of a plant. (a and b, about 150: 1; c, 250: 1). in superiori parte instructa, ramulos sporangiferos, 1 — 2 raro plures cellulas continentes gerentia, ad apicem versus leniter attenuata ex cellulis cylindricis in inferiori parte filorum 5,5// F. Børgesen : Rhodophyceæ of the Danish W. Indies. 27 At the base latis 10 pi longis, in superior! fere 2 fi latis et 20 // et ultra longis composita. Chromatophorum parietale, pyrenoide lateral! munitum. Monosporangia aut sessilia aut pedicellata aut in ramulis posita oblonga, 14 — 16 ^i longa, 6 — 8// lata. The base of the plant (Fig. 19 c) consists of creeping epi- phytic filaments which are mostly free or somewhat fused together. The cells in the basal part are about as long as broad or a little longer. They are 5,5 ^ broad. From the cells in this disc erect filaments arise, these filaments (Fig. 19 a, b) are about 5,5/^ thick; they taper slowly towards the summits and often end with long hair-like prolongations in which the cells are only about 2// wide. In the lowest part of the filaments the cells are about 10// long, in the upper end on the other hand they often reach a length of about 20 /^ and more. The chromatophore (Fig. 20) is parietal with irregular prolongations and contains a large pyrenoid lying near the wall of the cell and protruding deeply into the interior of the cell. The filaments are not much branched, often not at all in the lowest part and bearing here for the most „. g. . part only short branches with sporangia. In the chætium gra- upper part the filaments give off multilaterally "^^ "°'^- ^P?*^- situated branches, mostly only a few and these ment with branches are as mentioned above often terminated sporangia. 1 1 • 1 • 1-1 1 • (About by thm hair-like prolongations. 800 : 1). The branchlets bearing the sporangia are mostly multilaterally placed upon the lower part of the principal bran- ches. But uniseriated branches also occur especially higher up in the filaments. Most of the branchlets are unicellular, bearing a single or sometimes two sporangia, but two-celled branchlets are also common while others with several cells are found more rarely. Sessile Sporangia are scarce but they occur now and then, especially in the upper end of the filaments. The sporangia (Figs. 19 a, 6, Fig. 20) are linear oblong, about 14 — 16 fj. long, 6 — 8 fJ. broad. This species was found upon old leaves of Sargassum vulgare growing here together with several other species. Only found once in the Harbour of St. Thomas. 28 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 6. Acrochætium globosum nov. spec. Thallus cæspitosus, globosus, ad 600// altus; in Chætomorpha antennina epiphyticus. Fig. 21. Acrochætium globosum nov. spec. Part of a plant showing tlie basal creeping filaments from which arise erei filaments with opposite sporangiferous branchlets. (About 100: 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 29 Discus basalis bene evolutus, unistratosus, e filis repentibus ramosis, cellulis fere isodiametricis, compositus. Fila erecta nume- rosa, parce ramosa, ad apicem versus attenuata et in pseudopila producta; in basi et media parte 5—6//, in superiori parte 2—3// crassa, cellulis inferioribus c. 14^«, mediis c. 30/<, superioribus 10 fj. vel plus longis. Chromatophorum parietale, pyrenoide laterali instructum. Ramuli sporangiferi numerosi, sparsi aut sæpe oppositi, 1 — 3, rarius plures, cellulas continentes. Sporangia ovata, 7—8// lata et 8—10// longa. This species was found upon Chætomorpha antennina upon which it forms small dense nearly globular or semiglobular tufts. The basal part (Fig. 21) of the plant consists of creeping ramified fdaments, more or less fusing together and forming in this way a large disc. The cells in the disc are rather irregularly shaped, about as long as broad or a little longer i. e. from 5 to 11 /< broad. From this basal part numerous erect fda- ments grow up ; those in the middle are nearly straight, those in the periphery are bent out- wards in view of space and light. At the base the erect filaments are about 5 — 6// broad and the length of the cells about 14/«. Upwards the length of the cells increases gradually reaching in the middle of the filaments about 30/«. From here the cells not only grow longer but the filaments also taper towards their summits in such a way that the uppermost cells only reach a breadth of 2—3/« while the length of the cells on the other hand is often more than 70/« (Fig. 21). These thin unbranched prolongations of the filaments are nearly or quite colourless and hairlike. While the lowermost cells in the filaments taper a little at both ends those higher up in the filaments are cyhndrical. The cells con- tain a slightly developed parietal chromatophore lying near the upper end of the cell and a lateral pyrenoid (Fig. 22). The erect filaments are multilaterally ramified but not much. These branches contrast distinctly with the numerous short sporangiferous branchlets. Along the whole length of the fila- ments from their base and up to the beginning of the hair-like prolongations nearly all the cells bear either a single or more Fig. 22. Acrochæ- tium globosum nov. spec. Part of a filament with branchlets bear- ing sporangia (some ones emp- tied), (about 600:1). 30 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. often two opposite branchlets (Fig. 21). In the lowest part of the plant these branchlets consist of 2—3, rarely more cells, higher up of two, then of a single one only ; at the top some few sessile sporangia may occur. The cells in the branchlets are about S/x broad and S/j. long. The sporangia are ovate about 7 — Sju broad and 8 — 10 ft long. This species has been found at the very exposed coast at Northside, St. Croix. 7. Acrochætium Sancti Thomæ nov. spec. Thallus sine pilis usque ad 200 — 300 /^ altus. Discus basalis unistratus, e fdis re- pentibus plus minus lateraliter confluenti- bus, compositus. Fila erecta sim- plicia aut parce ra- mosa, e cellulis 8 — 9// latis et 16 — 18// longis composita. Chromatophorum parietale, pyrenoide, ut videtur, centrali instructum. Pili longi hyalini, initio terminales, po- stea pseudolaterales, adsunt. Monosporangia plerumque sessilia et uniseriata, interdum pedicellata et oppo- sita, solitaria vel bina in uno articulo, ob- ovata, 7 // lata et 10 fj. longa. This plant was found together with T.. oo ^ , • c^ ■ rr.j several other species Fig. 2ö. Acrochætium Sancti I homæ nov. spec. i i i e a, b, c, three parts of different tufts showing upon old leaves ot sporangia-bearing filaments, d, e, bases of Sargassum vulgare plants, f, basal filaments seen from above. p • n . p. (a, about250:l,fc,c,e, 130:1, /•, 250:1, rf, 500:1). formmg small tutts. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 31 The base (Fig. 23 d, e, /) consists of creeping filaments irregu- larly ramified and more or less fusing together into a pseudo- parenchymatous disc. From most of the cells in the creeping filaments erect ones are given off. These filaments are composed of ceils nearly twice as long as broad, 8 — 9 jj. thick and 16 — 18^ long; the lowest are nearly cylindrical, higher up in the filaments the cells are more barrelshaped being somewhat swollen in the middle (Figs. 23 a, 24). The cells contain a large parietal chromatophore with long lobes along the walls of the cells (Fig. 24) and with a pyrenoid lying near the middle of the cell. The shape of the chromato- phore seems to come near to that Rosenvinge found in A. (C.) leptonema. The cells are mostly very rich in starch filling up the greater part of the lumen making it difficult to see the shape of the chromatophore. The filaments are mostly slightly ramified, often not at all. However, the more vigorously developed filaments sometimes give off branches like themselves. Short branchlets on the other hand are often present (Fig. 23 a). The cells bear often long, hyaline, unicellu- lar hairs (Fig. 23 b, c). These are at first termi- nal on the end of the filaments but later on they are pushed to the side by the next new cell in the way described for several species by Kylin and Rosenvinge, and the sympodial na- ture of the filaments was clearly visible in this species. The hairs are thickest near the base, here about 4/^ broad, tapering towards the summit where their diameter is only about 2 // long ; they reach a length of about 200 — 300^. The hairs are quite hyaline with the ex- ception of the uppermost end which is richly provided with contents. They seem to be rather early shed. The monosporangia are mostly sessile, arranged in series upon the upper end of each cell in the filaments, some are pedicellate, placed upon the short branchlets mentioned above (Fig. 23 a). The sporangia are oval-obovate in shape (Fig. 24 a), about 1 fjt broad and 10// long. This species is certainly nearly related to Acrochætium leptonema Fig. 24. Acrochæ- tiumSancti Thomæ nov. spec, a, sum- mit of a filament with sporangia. 6, cells from lower down in a fila- ment with chro- matophores and nuclei. (About 500 : 1). 32 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Rosenv.; but to judge from the figures of Rosenvinge the habit of his plant is very different from the mine. Further the filaments in his plant are only half as broad as those in my plant and the sporangia also are somewhat smaller. Only found once: St. Thomas, The Harbour. 8. Acrochætium seriatiim nov, spec. Thallus cæspitosus usque ad 1 mm altus e disco basali in fila- mentis hospitis epi- phytico et filis erectis ramosis constructus. Discus basalis uni- stratosus,e filis repen- tibus confluentibus, cellulis brevibus fere isodiametricis irregu- lariter formatis com- positus. Fila erecta a basi quoquoversum ramosa in superiori parte secundatim ra- mosa, ramis principalibus vix, minoribus plus minus ad apicem versus attenuatis. Cellulæ in parte basali ca. 22^« longæ, diametro ca. 8 — 10;/ lato, in superiori parte diametro ca. 6 — 1 [i, interdum 4/i lato, et ad 30// longæ, chromatophorum parietale lobatum, pyrenoide laterali instructum continentes. Fig. 26. Acrochætium Sporangia ovalia, 9—10—13 ^ longa et seriatum nov. spec. Base ß — 9« lata, sessilia aut interdum pedicel- of a plant seen from i , • i . • • i ^ above. (About 400:1). J^^a, in latere superiori ramorum plerum- Fig. 25. Acrochætium seriatum nov. spec. a, b, erect filaments with monosporangia. c, base of a small plant seen from above, d, transverse section of the base; the lines at both end are the surface of the host plant. {a, b, about 130:1; c, 400:1; d, 275:1). F. Børgesen: Bhodophyceæ of the Danish W. Indies. 33 que secundatim ordinata, rarius plus minus sparsa. This species is an epiphyte especially upon Centroceras but it is also found upon other algæ e. g. Gracilaria, Chætomorpha, Caulerpa taxifolia etc. It forms small more or less dense tufts from 500 fx up to double this height. The basal part (Fig. 25 c, Fig. 26) con- sists of short irregularly bent creeping filaments, fusing together in the middle into a small disc; it is composed of short rather thickwalled cells. From the cells in the middle of this disc several erect filaments gradually arise. The filaments consist in their lower parts of cells about twice as long as broad, namely 8—10// broad and 16— 22/i long. Upwards the filaments taper gradually, reaching near the summit about 6 — 7 //, while the length of the cells is mostly about the same throughout the whole fila- ment, but thinner branches occur in which the cells are only about 4// broad while on the other hand the length may reach up to SO [J.. The erect filaments are branched often from quite near the base, in the lower part from all sides, higher up often quite uni- laterally with the branches lying in the same plane; the branches are again rami- fied in the same way (Fig. 25 a) ; from this the plant often gets an elegant pectinate appearance. The cells contain a parietal chromato- phore often with Jong prolongations along the wall of the cells and with a large lateral pyreiioid much protruding into the interior of the cell (Fig. 28) ; in some speci- mens the chromatophore is large covering riMum nov. spec. nearly the whole wall with the exception ^^^^.''^t' witV 'spi^angi^^' of a small part near the ends of the cells; A(bout 135 : l). Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1915). 3 Fiff. 27. Acrochætium se- Habit 34 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. in others it is reduced to an often narrow belt lying a little above the middle of the cell. The sporangia are monosporous, oblong- ovate, 9—11—13// long, 6—9, mostly 7—8// broad. They are as a rule sessile and usually secundly seriated in long rows placed on the inner (upper) side of the branches from the base upwards (Fig. 25 a); but more scattered sporangia also occur (Fig. 27) just as pedicellate sporangia are by no means rare. The present plant has a great likeness to Chantransia Hypneæ but this differs in having Fig. 28. Acrochæ- endophytic basal filaments. Further it is also «mm s^ia« urn no V. pgig^^^g^j \^q Acrochætiiwi flexuosiim Vickers. But ments with spor- in this plant the monospores are secund upon ^^^?50 .^f;^°^^* short ramuli, while in the present the ramuli are wanting, the monospores being placed in long series upon the branches. This species has been found mostly in more sheltered localities. It seems to be common. St. Croix: Coakley Bay, Christians- sted, Lt. Princess, Sandy Point; St. Tho- mas: The Harbour. 9. Acrochætium flexuosum Vickers. Vickers, A., Liste des Algues de la Barbade. (Ann. sciences nat. IX Sér., Bot. 1905, vol 1, p. 60). A quite certain determination derived from the somewhat imperfect diagnosis of M"'' Vickers seems impos- sible, and had the plant I now suppose to be this species not grown upon Chætomorpha antennina it had perhaps not occurred to me to refer it to this species. The plant found forms dense tufts about 700 /i high; it has a large base Fig. 29. Acrochætium flexuosum composed of creeping filaments more Vickers^ a.^part^o| a.fflament or less fusing together in the inner angia. b, a young plant. ^^Yi. («. about 125:1. b, about 160:1). F. Børgesen: Rbodophyceæ of the Danish W. Indies. 35 Fig. 29 b shows a supposed yoimg plant. The germinating spore has given off a single cell, the earliest beginning of the creeping basal filaments, and from this cell an erect filament arises. In the full grown plant a great number of erect filaments grow up from the inner part of the basal part ; those in the middle are straight, those in the periphery are bent outwards. In the lower part the filaments are about 9 — 10/^ broad tapering somewhat towards the summit where the diameter of the cells is only about 6 — 7 fi. The cells are about 2 — 3 times as long as broad in the basal part, reaching a length of about 18 — 35//; in the upper part the length is about 30 — ?>b ft. The cells contain a parietal chromatophore (Fig. 30) with longer or shorter prolongations along the wall of the cell and a large lateral pyrenoid protruding greatly into the interior of the cell. The sporangia are situated upon small secund mostly two-celled branchlets (Fig. 29 a) ; they are placed on the upper, inner side of the branches upwards from the axils. They are ovate-oblong (Fig. 30) ; 14 — 16// long and 9 — 10 /< broad. This species is evidently nearly related to Acrochætiiim Sagræaniim Bornet i). I have compared my specimens with the large plant distributed in Phycotheca Bor.-Am. Nr. 39 under the name of Chantransia Fig. 30. Acrochætium flexuosum Vickers, a, part of a filament with sporangia - bearing virgatula and upon which Bornet has partly branchlet. b, a spor- based his description of this species. But ^"^'"JioTt'TOrir""^" the present species is \ much smaller and differs among other things by having proportionally shorter cells. This species seems to be common upon Chætomorpha antennina of which the ends of the filaments often are red coloured by the epiphyte. St. Croix: Northside. Geogr. Distrib. : Barbados. 10. Acrochætium unipes nov. spec. Thallus usque ad 2 mm altus, a basi ad apicem versus attenuatus. Spora germinans, deorsum prolongationem subsphæricam endo- ^) Bornet, E., Deux Chantransia corj/mbiferaThuret. Acrochætium et Chan- transia (Bull. Soc. Bot. Fr., t. 51, 19ü4, p. XXI). 3* 36 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. phyticam in cellulas hospitis, sursum filum erectum sporangiferum emittens. Filum erectum a basi nudum in superiore parte ramosum ramis sparsis plus minus ramosis. Cellulæ cylindricæ in inferiori Fig. 32. Acrochætium unipes nov. spec. Base of a plant. (About 450 : 1). Fig. 31. Acrochætium unipes nov. spec. A whole plant showing the basal cell and the erect ramified filament with sporangia- bearing branches. (About 70 : 1). Fig. 33. Acrochætium unipes nov. spec. Bases of two plants; a, seen from above, b, in verti- cal section. (About 200 : 1). parte ca. 11 — 12;/ latæ, 50// longæ, in superiori fere 5// latæ, 50 — 60// longæ, chromatophorum parietale, pyrenoide laterali instructum continentes. Sporangia in filis lateralia, uniseriata, sessilia, oblonga, 9 — 11^« lata et 20 — 22// longa. F. Borgesen : Rhodophyceæ of the Danish W. Indies. 37 This species was found in a depth of about 10 meters i) growing upon Dictyota linearis. The largest specimen found had a length of up to 2 mm. The base of the plant consists of the original spore which during germination penetrates into the epidermal cells of the host forming a process (Figs. 32, 33) ; this is thinnest in its upper end where it passes through the wall of the host broad- ening more out downw^ards getting a somewhat obovate-clavate shape, by means of which the plant becomes more strongly fixed to the substratum. The process reaches in all a length of about 35// and reaches often the lower wall in the cell of the host plant. The spore itself lies freely above the wall of the host plant; it is nearly spherical with proportionally thick wall ; its diameter reaches a length of about 20—22^. From this basal body a single erect fdament grows upwards ; once only did I find two filaments arising from it (Fig. 33 b) ; but in this plant the primary filament had been destroyed and then another one was given off at the side of the first one. The erect filament is straight and at first not branched, higher up bran- ches are given off to all sides (Fig. 31) ; these are also very straight and issued from the principal filament in an acute angle and most often branched in a similar way. Against their summit all the filaments taper somewhat. The cells in the principal filament and the lowermost cells in the branches are cylindric, somewhat thick-walled, their dia- meter reaching a length of about 9 — 11// and their length up to 50//- In the summit on the other hand the cells are only about 5// thick while their length is about 50 — 60//. The cells contain a parietal chromatophore with a pyrenoid lying at the wall (Fig. 34). The monosporangia (Figs. 31 and 34) occur upon the inner 1) By a misprint is the depth in Part II (Dansk Bot. Arkiv, Bd. 2, Nr. 2, p. 54 [Reprint p. 210]) said to be 40 meters. Fig. 34. Acrochætium unipes nov. spec. Part of the thallus with sporangia. (About 425:1). 38 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. side of the lowermost part of the branches; they are in the specimens found always uniseriated and sessile. The sporangia are oblong clavate reaching a length of about 20—22/^ and a breadth of 9—11/^. The sporangia found were apparently not quite ripe. To judge from the description of Acrochætium Hoytii Collins i) this plant seemingly comes near to my plant. Acrochætium Hoytii seems to have a very similar base, but it has 1—3 erect filaments which only reach a diameter of about 6 n ; further it appears to be more branched and the sporangia are pedicellate and much smaller than those in my species. I wished very much to compare my plant with that distributed in Phycotheca Bor. -Am., No. 1540 and have also examined the material distri- buted but did not succeed in finding the plant in the material to which I had success. Acrochætium unipes has only been found once in a depth of about 6 fathoms. St. Croix: Frederikssted. 11. Acrochætium opetigenum nov. spec. Thallus 1 — 2 mm altus. Spora germinans globosa, processum decumbentem cuneiformem in cortice hospitis {Dasyæ elegantis) endophyticum et filum erectum sporangiferum procreat. Fila erecta, a basi ramosa, cellulis cylindricis ad 80// longis, ad basin ca. 8 — 11^ latis, in media parte 13 — 14// latis ad apicem versus paulo attenuatis ca. 6— 7/i latis. Ghromatophorum parie- tale pyrenoide laterali instructum. Ramificatio uberrima, rami sparsi. Monosporangia sessilia aut pedicellata ad basin ramorum 2 — 3 præsentia, oblonga vel subcylindrica, c. 11 // lata c. 27// longa. This species is the largest Acrochætium found on the shores of the islands ; well grown specimens reach a height of up to 1 — 2 mm or more and form a dense much branched tuft. The base (Fig. 36) consists of the original spore from which an elongated cuneate prolongation grows downwards and pene- trates into the tissue of the host plant {Dasya elegans). ' This endophytic part reaches a length of about 20//. In some plants, especially the older and more vigorous (Fig. 36 h) is furthermore developed one or a few short horizontal 1) Collins, F. S., Two new species of Acrochætium (Rhodora, vol. 10, 1908, p. 134). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 39 filaments from the lowermost part of the spore. These fila- ments consist of a few cells only and lie along the surface of the host in which they are not imbedded, or at the most only a little on their lower side. From the cells in these creeping filaments erect ones were found growing up in a few vigorous specimens (Fig. 36 b). The spore itself is quite globular, about 17// in diameter; it lies upon the surface of the host plant. The plants are mostly fixed at the base of the pinnules of the host and many plants are often found surrounding each pinnule (Fig. 36 a). Most probably the ger- minating spore finds more shelter here. But plants occur also on other parts of the host and even upon the pinnules them- selves. From each spore a single (or in more vigorous plants two or more) erect filaments grow up. They consist of cylindric cells ; ' in the basal part their diameter is about 8 — 9 — 11 yt, higher up the diameter increases and in vigorous plants it reaches a length of 13—14 [x. The length of the cells is often 80 fi and more. Towards the sum- mit the filaments again taper, their diameter reaching only 6 — 7/i, but the ends are not hairlike and the cells contain both chromatophore and pyre- noid (Fig. 35). The chromatophore (Fig. 37) is parietal, often with long prolongations along the wall of the cell and it contains a large lateral pyrenoid protruding markedly into the interior of the cell. The ramification begins from near the base but is further developed higher up. It is multilateral and the branches ramify copiously in the same manner. The sporangia (Fig. 35, 37) are oblong-oval or more elong- ated, subcylindric or subclavate. They are mostly sessile but Fig. 35. Acrochætium opeligenuin nov. spec. Small part of an erect ramified filament. (About 90 : 1). 40 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. pedicellate examples also occur. The spor- angia are placed upon the lowermost cells of the branches mostly only two or three upon each fila- ment ; but they also occur upon the main Fig. 36. Acrochsetium opetigenum nov. spec. filaments. a, Transverse section of Dasya elegans with basal COLLINS has de- parts of three plants two of which fixed to the base -r. Arrorhjp- of a pinnule and showing the cuneate endophytic sciiüeu dii Jiuuutai process penetrating into the tissue of the host and tium {A. Dasyæ) also one fixed to the pinnule itself, b, basal part of an pi nn^im older vigorous plant showing the endophytic cuneate ^^unu upon jjubya process and further two short epiphytic branchlets ; elegans which seems from that to the kftjn^^erect ^filament is issued, ^osely related to the present species. It has for instance the same globular persistent basal spore but this emits, as described by Collins, "a short, descending process, some- times branched, of a few small rounded cells, attached to the host". I have examined the specimens, distributed in Phycotheca Bor. -Am., No. 1342 and have seen these short, 2 — 3 celled branches. As far as I can observe these branches are not endophytic and they are upon the whole quite different to the descending process found in my plant. Besides this difference my species has a very different appearance, is much larger in all parts of the thallus, much more branched and the ramification is not secund. Found upon Dasya elegans in a depth of about 20 meters. St. Jan: Off Cruz Bay. 12. Acrochætiuin robustum nov. spec. Thallus cæspitosus, usque ad 1 mm longus, e filis erectis et fihs horizontalibus epiphyticis compositus. Spora germinans in texturam hospitis pau- lum penetrans ; a superiori parte, non immersa, fila brevia repentia, plus minus lateraliter con- Fig. 37. Acrochse- tium opetigenum nov. spec. Sporan- gia-bearing filaments with chromato- phores and pyreno- ids. (About 400:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 41 Fig. 38 nov. Acrochætium rohustum spec. Base of a plant. (About 450: 1). fluentia, egrediuntur, et sic discum basalem formant, ex cellulis brevi- bus, diametro fere æquilongis, pariete crasso compositum. Fila erecta a basi ramosa, apicem versus sensim pau- lum attenuata, in parte basali 9 — 10// lata, superne ca. 5 n. Cellulæ cylin- dricæ 9 — 10// latæ, inferiores 15 — 20 fjL longæ, superiores ca. 40 [i longæ, chromatophorum parietale, pyrenoide laterali instructum continentes. Rami sparsi, nonnunquam secun- dati, ramulis sparsis, uni-, bi- aut tri- cellularibus, monosporangia gerentibus instructi. Sporangia ovata, ca. 11 /« lata et 12 — 14// longa. This species was found together with several other species upon old leaves of Sargassum vulgare. The base (Fig. 38) of the plant consists of a pluricellular disc composed of thick- walled cells. From this an unicellu- lar, thickwalled process grows down- wards fixing the plant strongly to the host plant ; how far these processes also should serve as haustoria like those described by Rosenvinge for Chantransia cytophaga, I have not been able to decide. The processes reach a length of about 20 fi ; the basal disc is about 8 — 10 /< thick. Not having succeeded in finding quite young plants I have not been able to follow the development of the basal disc, but most seemingly the germinating spore produces the process during germination (com- pare Fig, 38) and this grows down- Fig. 39. Acrochætium robustum ^^Yds in the tissue of the host nov. spec. Habit of a plant. (About 140 : 1). plant ; afterwards from its upper end 42 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. short horizontal filaments grow out which fuse together forming the disc. From the cells in the disc gradually several erect ramified filaments grow upwards forming a dense tuft (Fig. 39). The principal filaments consist in their lower part of short cells about l^/g — 2 times as long as broad, their diameter reaching a length of about 9 — 10 /i; upwards the filaments become gradu- ally thinner and the cells at the same time longer. Near the summit they are only about b fx thick and often upto 40^ long or more. Sometimes the cells in the lower part of the principal filaments are a little broader in the middle tapering towards both ends. The chromatophore (Fig. 40) is parietal often with some longer prolongations along the wall of the cell and contains a large pyre- noid projecting somewhat into the interior of the cell. The ramification of the filaments begins near their base, but on the whole the filaments are not much branched. Branches are given off to all sides but often with long interwalls. Two kind of branches are present, long fila- ments like the principal ones and short branch- lets upon which the sporangia are borne. The branchlets are as a rule one- or two-celled ; in the first case it bears a single terminal sporangium, in the latter the lower cell also bears a mostly pedicellate, more rarely sessile, sporangium. The last mentioned branch- lets occur mostly in the lower part of the tufts, while the first mentioned as a rule are only present in the upper part. Only rarely are the sporangia seated directly upon the main filaments. Branchlets with more than two cells are rare. The sporangia (Fig. 40) are monosporous, oval-ovate, about 11// broad and about 14 — 16// long; they are provided with a very thick wall, often up to 2/j. thick. This species seems at first sight to come near to Acrochætium Hypneæ ; but it differs in a different arrangement of the spores, these being sessile and seriated in Acr. Eypneæ; further Acr. Hypneæ has endophytic filaments which I have not found in Fig. 40. Acrochæ- tium robustum nov. spec. Part of a fila- ment with sporan- gia-bearing branch- lets. (About 700:1). F. Børgesen : Rhodophyceæ of the Danish W. Indies. 43 the present species, and the sporangia are rounder and have not the thick wall of Acr. robustiim. Found upon Sargassiim vulgare in sheltered place. St. Thomas: The Harbour. 13. Acrochætium bisporum Borgs. Chantransia bispora Borgs., Some new or Httle known West Indian Florideæ, II ("Botanisk Tidsskrift", vol. 30, 1910, p. 178). IUI OOO Fig. 41. Acrochætium bisporum Borgs. A, part of a plant with sporangia with two spores. B, part of a plant with monosporangia. C, sporangia with two spores. Z>, cells with chromatophore and pyrenoid. E, a young plant. F, G, H, I, basal parts of plants. {A, B. about 120 :1, F, G, I, about 250:1, C,D,E,H, about 350:1). In the former description of this plant, I have pointed out that it is perhaps nothing more than a variety of Acrochætium Hypneæ. I had hoped when looking through my collections to refmd it again and by a renewed examination be able to settle this question. 44 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. But unfortunately I have not been successful and therefore I am forced to adhere to my former position. As there men- tioned this species was found upon Acanthophora spicifera (Vahl) Børgs. From the basal cell which to begin with is roundish and thickwalled (Fig. 41 E) short creeping fdaments grow out ; some of these are epiphytic creeping upon the surface of the Acantho- phora, others penetrate into the tissue of the host-plant (Figs. 41 F, G, H, I) but it sometimes happens that young plants occur which are not at all parasitic. From the basal layer several erect fdaments gradually arise. The cells are usually a little constricted at the cross-walls; they contain a well-developed parietal chromatophore with a large lateral pyrenoid. The cells are about 8^ broad and about 20// long and mostly 21/, times as long as broad with some variations. The filaments are usually only slightly branched in the lower part, more so higher up; the side-branches grow out at an acute angle from the mother-branch and in well-developed plants the branches are again multilaterally ramified. Most of the specimens had monosporangia ; these are ovate- oblong, 6/z broad and 10// long, as a rule sessile, more rarely pedicellate, serially arranged upon the upper side of the branches. Sporangia divided into two spores were only found in few plants ; these are larger than the monosporangia, oval, about 9/< broad and 14// long; they are mostly sessile, sometimes pedicellate or placed upon short branchlets. In my former description I remarked that a single sporangium was found in which the upper half was again divided by a vertical wall. How far this suggests that the plant in reality has tetraspores, the specimens found representing only a young state of development, can only be settled by means of more material. Acrochætium bisporwn has been found only once, in the Harbour of St. Thomas. Geogr. Distrib., Danish West Indies. 14. Acrochætium occidentale nov. spec. Thallus usque ad 1 — 2 mm altus, e fdis erectis ramosis spor- angiferis et filis endophyticis constructus. Spora in filamentis assimilatoricis hospitis germinans, magna, ovata — globularia, e parte basah fila circum filamenta hospitis repentia, e parte superiori filum erectum singulum gignit. Filum erectum inferne nudum media parte ramosum, ramis sparsis ad apicem versus attenuatis instructum. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 45 Cellulæ cylindricæ in inferiori parte filorum ca. 11// latæ 40// longæ, in superiori 7—8// latæ 40 /j. longæ, chromatophorum parietale, pyrenoide laterali, instructum continentes. Sporangia sessilia, raro pedicellata in parte basali ramorum uniseriata, monospora aut raro hispora, ovalia, ca. 18 — 20/i longa et 9 — 12« lata. The basal part of this species is immersed in the mucilage and chalk incrustation of the host plant [Liagora elongata). On germination the spore does not divide and remains throughout undivided ; its diameter is about 16//. After the germination it produces endophytic fdaments from its lower side ; these creep downwards fixing themselves to the assi- milating filaments of the host plant (Fig. 42 c). From the upper end an erect filam.ent (or sometimes two) is given off (Fig. 42 a) ; this is at first undivided but after having grown so that it is quite free of the Liagora tissue it becomes branched. The ramification is some- what slight. The branches are given off at an acute angle and the branches themselves are ramified in the same way giving the plant a cluster-like appearance. Towards the summit the branches taper into hair-like filaments the cells of which are long and nearly colourless and soon die away at the end (Fig. 42 a). The cells in the filaments are about 10 — 11 /i thick and about 27 — 40// long; near the base the filaments are a little thinner, about 8 // ; in the hairlike ends the cells taper to about 7—8,«. The chromatophore (Fig. 43) is parietal, often with elongations towards the wall of the cell and it encloses a lateral pyrenoid. The sporangia (Figs. 42 «, b, Fig. 43) are sessile, oval-ovate. They are about 9 — 12 ß broad and 18 — 20 a long. Monosporangia mostly occur, but in a few specimens some were divided by a transverse wall into two spores (Fig. 43). It is perhaps not impossible that Acrochæiium Barbadense Fig. 42. Acrochæ- tium occidentale nov. spec, a, erect filament with spor- angia, b, part of a filament with spor- angia, the upper- most divided into two spores, the lowermost emp- tied, c, base of a plant fixed to the assimilating fila- ments of Liagora. {a, about 125 : 1; b, 250:l;c, 200:1). 46 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 43. Acro- chætium occi- dentale nov. spec. Branch with sporan- gia, the upper- most divided into two spo- res. (About 400: 1). (Vickers) is the same as this species. But the descrip- tion of M^i^ Vickers is so defective that any identifica- tion by help of it is impossible and as: "Les échan- tillons, mal conserves, ne se pretent pas bien å rétude", any help from the original material seems also excluded. The bases of the two plants in question are apparently alike and they are both living upon Liagora. Bornet and M^^^ Vickers refer the plant to Chantransia which suggests that the plant from Barbados had sexual organs ; these I have never found in my plant. As to the arrangement of the monospores of Acr. Barbadense, their form and size nothing is said just as no description is given of the sexual organs. St. Croix: Long Point. 15. Acrochætium comptum nov. spec. Thallus usque ad 1 mm altus et ultra, e filis erectis ramosis sporangiferis et fills endophyticis compositus. Spora in filamentis assimilatoricis hos- pitis germinans, magna, oblonga, in cellu- las duas divisa est ; e cellula inferiori fila decumbentia circa filamenta hospitis repentia, e cellula superiori filum singulum erectum gignitur. Filum erectum inferne nudum, superne ramosum ramis vicissim plus minus ramo- sis ramos seriates gerentibus instructum. Cellulæ cylindricæ 8 — 11 fi latæ, ca. 35 ju longæ, chromatophoro parietale pyre- noide laterali instructæ. Sporangia monospora, plerumque ses- silia, nonnumquam in ramuhs unicellu- laribus posita, singula vel bina, in parte basali ramorum uniseriata, ovata, 11 — 14 /i lata et ISn longa. This species is characterized by the ^ig. 44. Acrochætium „ , j^, ^ j^i . ,. •,•'•,! compzum nov. spec. Basal iact that the germmatmg spore is divided part of a plant showing by a transverse wall into two cells from the original spore divided .1 i> 1 • 1 J m . into two cells. (About the upper oi which an erect filament 350 . i)_ F. Børgesen : Rhodophyceæ of the Danish W. Indies. 47 grows upwards, while from the lower endo- phytic filaments growing downwards are produced (Figs. 44, 45 c and d). The last mentioned fdaments grow downwards round the assimilating filaments of the Liagora upon which the spore has germinated. They do not penetrate into the cells of the host plant but only into the mucilage and chalk incrustation found between the filaments. The main filament arising from the germinating spore remains in most of the specimens undivided in the basal part (Fig. 45 a), but specimens were found in which a single or few branches were given off from near the base. In some of the more adult specimens erect filaments were found growing up from cells in the des- cending filaments (Fig. 44). On one occa- sion a descending filament was found growing out from a cell near the base of the erect filament (Fig. 44). The cells a, haMt of erect, ramified in these are about 8— 11 « broad and their ^ament with sporangia •^ 0, part of plant with length about 35//. - - - When the erect filaments have grown long enough to become free of the Liagora they begin to branch more freely. The branches issue from the upper end of each cell mostly in an uniseriate manner; these branches bear again branches arranged secundly. Towards their apex the branches are undivided tapering somewhat becoming about 8 fj. thick, at the same time the chromatophores are not so well developed. The chromatophore is parietal (Figs. 44, 46) with a large pyrenoid. The sporangia are broad oval and mostly pedicellate (Figs. 45 a, b, Fig. 46), placed upon FigACy.Acrochæ- g^ort secund branchlets beins: seriately arranged liuin comptum o j » nov. spec. Part upon the upper, inner side of the branches. The °^.,,^ ^'^^'"^•'^* branchlets are as a rule one-celled and bear with sporangia. (About 4(1(1:1). mostly a single sometimes two sporangia. Sessile Fig. 45. Acrochætium comptum nov. spec. sporangia, c and d, bases of plants, (a, about 50 : 1 ; b, 250 : 1 ; c and d, 150: 1). 48 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. sporangia also occur often rather numerous especially in the upper part of the plant. The diameter of the sporangia is about 11— lA/jL, the length about 18//. This species has been found upon Liagora pinnata. St. Croix: White Bay. 16. Acrochætium Avrainvilleæ nov. spec. Thallus cæspitosus usque ad 1 mm altus. Pars basahs ex interiori parte plectenchymatis hospitis emergens, ex filis brevibus in filis hospitis externe repentibus composita. Tola planta a basi ad apicem sensim attenuata. Fila erecta, a basi simplicia, in superiori parte ramosa, ramis multi- laterahbus, rectis, plus minus ramosis instructa. Gellulæ cylindricæ, in parte basali ca. 9 fi latæ 33// longæ, ad apicem versus ca. 4/« latæ 50// longæ, chro- matophorum parietale, pyrenoide late- rali instructum continentes. Sporangia sessilia aut interdum pedicellata, sparsa aut pauca seriata, oblonga, 11 /j. lata, 22 jm longa. This plant was found upon an old specimen of Avrainvillea nigricans. The basal part of it was fixed to a filament of the host plant lying rather deep in the cortical plectenchyma (Fig. 47 a) ; on account of its very loose texture the Acrochætium has no difficulty in growing out through it, and as I have only met with two specimens of it in all I dare not deny the pos- sibility that the Acrochætium might be found quite epiphytic upon the external filaments of the host. The basal part consists of short, creeping filaments attached to the surface of the filaments of the host plant; they consist of proportionally short and thick-walled cells. From the cells in the middle of the basal filaments the erect ones are given off (one or more). At their base the erect filaments are unbranched (Fig. 48) ; Fig. 47. Acrochætium Avrain- villeæ nov. spec, a, filaments of Avrainvillea nigricans with the basal part of the Acro- chætium. b, base of the same plant more magnified. (a, about 40:1; b, 700:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 49 higher up when they have become free of the host plant do they begin to branch. They are multilateraliy ramified and the branches are straight and given off from the axis at an acute angle. The principal filaments are thickest near their middle or a little above where the ramification begins ; here the diameter of the cells reaches a length of about 9 /^. At their base the cells are only about 5,5 fi thick. Towards the summit the branches taper^again, the cells here becoming thinner and at the same time longer and with less contents. The cells are cylindri- cal, not constricted at the transverse wahs, in the basal part about 33 [j. long, while near the summit on the other hand their length can reach 50// or more. The chromatophore (Fig. 49) is parietal, often not much developed and contains a large lateral pyrenoid projecting greatly into the interior of the cell. 49. Acrochsetiwn Avrainvilleæ nov. spec, a, part of a filament with sporangia. Fig. Fig. 48. Acrochsetiwn Avrain- villeæ nov. spec. Habit of erect ... - - , ramified filament with sporan- b, cell with chromatophore and pyrenoid. gia. (About 70:1). (About 600 : 1). The monosporangia (Figs. 48, 49) are sessile or more rarely pedicellate, usually occurring on the inner side of the branches near their base, seriate or a few together; but sometimes more irregularly. Dansk Botanisk Arkiv, Bd. 3. Nr. \ (1915). 4 50 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 50. Acrochætium hormorhizuin nov. spec. Base of a plant. (About 250:1). The sporangia are oblong, about 22 ^ long and 11 fi broad. Found once only in deep water (about 20 meters). St. Jan: Off Cruz Bay. 17. Acrochætium hormorhiziim nov. spec. Thallus cæspitosus usque ad 1 mm altus et ultra, e filis endophyticis brevibus horizontalibus ramosis et filis erectis, a basi ramosis, spor- angiferis constructus. Fila endophytica in ex- teriorem partem membranæ cellularum hospitis {Champiæ parvulæ) penetrantia, ex cellu- lis brevibus pariete crassiori composita, discum basalem minorem supra ceilulas maximas hospitis formantia. E disco basali fila erecta creantur, ramis numerosis plus minus ramosis sparsis in superiori parte filo- rum uniseriatis. Cellulæ in inferi- ori parte filorum dia- metro fere 4 — 5-plo longiores, 9 — 11 // latæ , in superiori parte 8 — 9/^ latæ dia- metro fere 7-plo lon- giores. Chromatopho- rum p'arietale, pyre- noide laterali muni- tum. Sporangia sessi- lia aut rarius pedicel- lata, sparsa aut pluria seriata, oblonga, fere 20 — 22 fj. longa et 10 — 11 /j. lata. This species was found on Champia parvula upon which it forms small cushions about 1 mm high. Fig. 51. Acrochætium hortnorhizum nov. spec. a, habit of a plant, b, filaments with sporangia. c, base of a plant seen from above, (a, about 70: 1; b, 150: 1; c, 250: 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 51 The germinating spore grows downwards through the thick peripheral wall of the host plant until it arrives at the more compact innerwall of the cells. Here it ramifies sending out some few short horizontal branches (Fig. 50). These consist of thick-walled cells nearly as long as broad or a little longer and much swollen in their middle part, the endophytic filaments thus assuming a moniliform appearance (Fig. 51 c). The length of the cells is about 12 — 14 fj. and the breadth about 11 fjt. From this endophytic basal part the erect free filaments arise (Figs. 50, 51 a, c). These are more or less ramified through their whole length, in the lowermost part on all sides, but higher up often uniserially ; they taper only slightly towards their summits. The filaments consist of cylindrical cells chætium hor- which at the basal part are about 9—11 ^ broad morhi^mnoY. and about 30 — 50 fx long, in the upper end 8 — 9 ^ flianient with broad and about 60 fx long. The branches ramify sporangia. repeatedly. All the branches are mostly rather straight. The cells contain a plate-shaped chromatophore (Fig. 52) with a well developed pyrenoid protruding somewhat into the interior of the cell. The sporangia (Figs, blh, 52) are mostly sessile but some are pedicellate. They occur as a rule upon the lowermost cells of the fila- ments seriate upon their upper side, but now and then also more scattered. The sporangia are ob- long-elliptic of shape, about 20—22 fx long and 10—11 fx broad. Found once only in a sheltered locality. St. Croix: Christiansteds Lagoon. Fig. 53. Acrochsetium H]jpneæ Børgs. Base of a plant. (About 300: 1). 18. Acrochætium Hypneæ Børgs. Chantransia Hypneæ Børgs., Some new or httle known West Indian Florideæ, I (Bot. Tidsskr., 30. Bd., København 1909). 4* Dansk Botanisk Arkiv, Bd. 3. Nr. 1. As pointed out in my former description this species is an endophyte growing upon Hypnea. I have examined it again and give now a new figure of the basal part (Fig. 53). As the figure shows the base consists of short horizontal filaments creeping in the thick wall of the host. The cells in these fila- ments are short, only a little longer than broad, and from these cells the erect sporangiferous filaments grow upwards often seve- ral together forming in this way small tufts upon the host. The erect filaments are not very richly branched (Fig. 54) ; the branches grow out at an acute angle from the mother branch. The ramification is multilateral with some tendency in the upper part to be secund. The cells are cylindrical, usually 2 — 4 times as long as broad. They contain a well developed parietal chroma- tophore (Fig. 54 b) covering nearly the whole wall of the cell and have a large lateral pyrenoid. The sporangia are seriate on the upper side of the branches, sessile or very rarely pedicellate. If the basal part is left out of consideration it can- not be denied that the above, described Acrochætiiim sena- tum shows great likeness to this species. But while the present plant has an endophytic base the other is epiphytic. This species has been found in a small lagoon with shallow water. St. Thomas: The Harbour. Geogr. Distrib. : Danish West Indies. 19. Acrochætium repens nov. spec. Thallus e fills endophyticis et fills sporangiferis erectis com- positus. Fig. 54. Acrochætium Hypneæ Borgs. A, plant with monosporangia. ß, cells with chromatophore and pyrenoid. C, D, E, hasal parts. (.4, about 125:1; B, C, about 250: 1; D, E 200: 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 53 Fila endophytica irregulariter ramosa sub cellulis epider- malibus hospitis horizontaliter repentia, e cellulis medio plus minus irregulariter inflatis constructa. Fila erecta, ad 500 // alta, ramosa, apicem versus sensim attenuata, e cellulis ad basin 7 — 8 // latis, superne 2 — 3 fi. latis, inferioribus c. 24// longis, superioribus c. 50// longis et subhya- linis constructa. Chromatophorum parie- tale pyrenoide laterali in- structum. Sporangia oblonga, 14/« longa et 8// lata in ramulis unicellaribus solitaria vel bina, raro sessilia adsunt. Fig. 55. Acrochætium repens nov. spec. Two erect ramified filaments with spor- angia and the basal creeping part. (About 300 : 1). Fig. .56. Acrochætium repens nov. spec, a and b, erect filaments with sporangia, c, endophytic, basal filaments seen from above. (About 260 : 1). This species was found upon a Gracilaria-like plant. The endophytic filaments creep below the surface cells of the host (Fig. 55), forming a nearly reticular expansion (Fig. 56 c). The basal filaments are irregularly ramified, consisting of barrel-shaped or more irregularly formed cells more or less swollen in the middle and much tapering towards both ends. 54 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Now and then from these cells erect filaments arise penetra- ting through the epidermal layer of the host plant (Fig. 55). The erect filaments reach a length of up to 500 /z. Below they are about 7 — 8,« thick and the length of the cells about 24^. Up- wards they taper gradually and end with long nearly colourless hair-like threads; the cells in these threads may reach a length of up to bO/u or more and are 2 — 3// thick. The erect filaments are multilaterally or very seldom oppo- sitely ramified and the branches taper in the same way into hair- like ends. The chromatophore (Fig. 55) is parietal with lobed margin and with a lateral pyrenoid often projecting considerably into the interior of the cell. The sporangia (Figs. 55, 56 o, b) are placed at the base of the branches or upon branchlets. They are nearly always pedi- cellate, but now and then the uppermost sporangium is sessile. The sporangia are oblong, about 14^ long and 8;z broad. Found only once in a sheltered locality in shallow water. St. Thomas: The Harbour. 20. Acrochaethim phacelorhizum nov, spec. Thallus cæspitosus ad 1 mm altus et ultra, e filis endophy- ticis et fihs erectis ramosis sporangiferis compositus. Fila endophytica inter assimilatores hospitis immersa, sæpe aggregata, in superiori parte ramosa, e cellulis ca. 40// longis et 22 — 25, raro 27// latis orta. Fila erecta, apicem versus sensim attenuata, a basi ramosa. Rami in superiori parte filorum numerosi, sparsi aut sæpe uni- seriati. Chromatophorum parietale pyrenoide laterali instructum. Monosporangia sessiha, sparsa aut seriata, oblonga, 12 — 14// lata, 22—24/« longa. This plant was found upon Codium elongatum and isthmocladiim among the utricles of which the basal part is immersed while the upper free-growing filaments form tufts about 3 — 4 mm high. Some small differences were present in my specimens; I shall first describe those found in Codium elongatum. The basal part (Fig. 57) consists of proportionally very thick filaments creeping downwards along the wall of the utricles and between them; in the uppermost end the endophytic filaments are ramified sending downwards from the lower end of the cells F. Børgesen: Rhodophyceæ of the Danish VV. Indies. 55 new endophytic filaments while upwards from their upper ends the assimilating and spore-bearing filaments arise. In this way the endophytic filaments form together proportionally dense clu- sters as most of the filaments run downwards nearly side by side ; but now and then also endophytic filaments are found which bend outwards to the side, thus giving rise to new tufts in a similar way to that described by Rosenvinge for Acrochætiiim Nemalionis. But in Acrochætiiim phacelorhiziim it seems to be not so common. The endophytic filaments reach a thickness of up to 27 fji and the length of the cells is about 36/^. Most often they are thickest at the lowermost end tapering gradually up- wards. The wall of the filaments is often somewhat sinuous. From the upper end of this rhizome- like base the erect filaments arise as men- tioned above forming a more or less dense cluster; in a vigorous plant about 4 — 6 filaments are present; the remnants also of several broken off or dead filaments are often to be found. The erect filaments (Fig. 58) have spreading branches, in the upper part with some tendency to unilaterality. The filaments are thickest in the lowermost part, about 11 — 12 fx, tapering very grad- ually towards their summit, being here about 6/z thick; these thin ends of the filaments die gradually away. In spec- imens still in vigorous growth the fila- ments have blunt ends and do not taper so much. In the lowermost part the cells are about 40 /x long, being mostly a little longer upwards, about biju. The cells are cylindrical and not constricted at the transverse walls. They contain a parietal chromatophore (Fig. 59) with a large pyrenoid protruding con- siderably into the interior of the cell. In the .specimens found the sporangia were not present in great number. They occur often a few together seriately near the base of the branches but, often also quite scattered (Fig. 58). All the sporangia found were sessile and monosporous, oblong, Fig. 57. Acrochæliwn phacelorhizum nov. spec. Two basal parts. (About 100 : 1). 56 Dansk Botanisk Arkiv, Bd 3. Nr. 1. about 12 — 14 /i broad and 22—25// long. At the sninniit of the sporangia a small thickening is often present (Fig. 59). The specimens found in Codium isthmocladum agreed in all essentials with those described above, but some small differences were noted. Thus the basal endophy- tic part of the plant was often looser, not so tufted together as shown in the fig. 57 and the endophytic filaments were a little thicker, about 33 fi. Also the erect filaments were somewhat thicker , at their base about 14 — Ibfj. thick, at the apex about 6—7;/. Several species of Acrocliætium occurring upon Codium have been previously described. The brothers Crouan have found the Acrochætium (Callithamnion) Codii ^) upon Codium elongatum. Of this species Dr. Ro- senvinge has ben able- to examine original ma- terial and has most kindly shown me a fine preparation from which it is clear that my plant has nothing to do with this species. Dr. Rosen- viNGE will later give a description of this plant. 1) Crouan, P. L. et H. M., Florule du Finistére, 1867, p. 135 (nomen nudum). Cfr. Bornet, Deux Chantransia corymbifera Thuret (Bull. See. bot. France, Tome 51, 1904, p. XX). Fig. 58. Acrochætium phacelorhizwn nov. spec. Uppermost part of the basal part with an erect ramified sporangiferous filament. (About 5U : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 57 !^ In "Forschungsreise S. M. S. »Gazelle«", IV part, Bot., p. 31 AsKENASY has described the Acrochsetium [Chantransia) Naumanni in which the sporangia seem to have a similar thickening of the membrane at their summit as in the present species, but in its whole appearance and in its way of growing, quite or nearly quite immersed in the host plant, it is very different from my plant. The Acrochsetium {Chantransia) interpositum Heydrich^) must be identical with Askenasy's species and is in any case highly distinct from my plant. Finally as to Callithamnion poly- rhiziim Harv.^), this plant also seems to be very different, Mr. A. D. Cotton has most kindly examined for me a little fragment of the ori- ginal plant of Harvey. From this it is evident that Harvey's plant is much larger and quite different from the mine having much likeness to Rhodochorton. Of species not found in Codiiim our plant has some likeness also with the Acrochsetium {Callithamnion) N emalionis De Notaris of which a very detailed description is given by Ro- senvinge (1. c. p. 126). But Acroch. Nemalionis ^ « has, as described by Rosenvinge, "long rami- f-^^- ^'^,- ^^tocä«- . ■ , 1 ■ 1 • tiuin phacelorhizuin lied filaments growing widely m the interior of nov.spec. a, filament with sporangia. the host and here and there sending out through the surface of the host free filaments giving rise to new tufts." This I have not found in my plant. And further in Acrochsetium Nema- lionis the sporangia are borne on branchlets while all I have seen in my species were sessile ces to which several others can be added show that my plant is very different from that of De Notaris. This species has been found at the shores of St. Croix: Coakley Bay {in Codiuin isthmocladum) and S t. J a n : Off America Hill (in Codium elongatum). (About 200 : 1). b, cell of the main filament with chro- matophore and pyrenoid. (About 250 : 1). These differen- 21. Chantransia Liagoræ nov. spec. Fila vegetativa endophytica inter filamenta assimilatoricis hospitis repentia, parce ramosa, ramis sparsis, ramulis brevibus instructis. 1) Heydrich, f., Vier neue Florideen von Neu-Seeland (Berichte d. deutschen bot. Gesellschaft, Bd. 11, 1803, p. (78), pl. XXII, flg. 8). 2) Harvey, W. H., Phycologia Austrahca, vol. V, 1863, p. LVI; compare also J. Agardh Epicrisis, 1876, p. 12. 58 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Cellulæ subcylindricæ, dolioformes, medio plus minus inflatæ vel interdum magis irreguläres, 8 — 14// latæ, ca. 35// longæ, chro- matopliorum stellare, pyrenoide centrali instructum continentes. Pili hyalini terminales, non numerosi, adsunt. Sporangia, sessilia aut pedicellata, sin- gula vel interdum bina, globulose-obovata, ca. 20// longa et ca. 14 /i lata. This species was found abundantly in Liagora pinnata. It creeps among the assi- milating fdaments in the mucilage and chalk coating found here (Fig. 60). The filaments are not particularly branched and rather long intervals occur which have no branches at all; in some parts of the filaments on the other hand branchlets are given off from the outer side of nearly each cell in the filaments (Fig. 61). Sometimes these branchlets are repeatedly ramified ; it also happens occa- sionally that two branchlets arise from the same cell. These branchlets bear the monosporangia, but sessile sporangia placed immediately upon the cells of the main filaments are not un- common. Fig. ()0. Acrochsetium Liagoræ nov.sTpec. Part of a plant between tlie assimilating filaments of Liagora. (About 120 : 1). Fig. 61. Acrochsetium Liagoræ nov. spec. Parts of three plants with sporangia (some ones emptied). (About lb:l and 200:1). The cells in the main filaments are irregular in shape, mostly somewhat swollen in the middle tapering towards both ends; in the middle their diameter reaches a length of about 16//, at the ends about 8//; their length varies about 35/r/. The chromatophore (Fig. 62) is stellate with long strands run- F. Børgesen: Rhodophyceæ of the Danish W. Indies. 59 ning along the walls of the cells; in their middle a well developed pyrenoid is present. The cells in the ends of the filaments bear now and then thin hyaline hairs (Figs. 60, 62); these are about 5,5/^ thick and reach a length of about 300 — 400 /i. Fiff 62 Acrochætium Liagoræ nov. spec. Part of a plant with sporangia ^' and hair. (About 400 : 1). As mentioned above the monosporangia are developed in the end of the branchlets or more rarely upon the main filaments; they are obovate-globular of shape, about 20// long and 14// broad. Of the species mentioned by Rosenvinge I think it comes nearest to Acrodiætiiim (Chantransia) Pohjidis Rosenv. This species has only been found once at the south coast of St. Croix. 22. Acrochætium ernothrix nov. spec. Thallus cæspitulosus, ca. 400// altus. Pars basalis non certo observata est. Fila erecta a basi ramosa. Rami principales stricti, in inferiori parte paucis, in superiori numerosis ramis et ramulis instructi. Cellulæ ramorum 5—6// latæ et 15—18/« longæ, cylindricæ, chromatophorum zonatum prolongationibus irregularibus instruc- tum et pyrenoide centrali munitum continentes. Ramuli sporangiferi e 2—3, rarius pluribus cellulis compo- siti, ad apicem versus angustati in pseudopila longa producti. Monosporangia sessilia aut pedicellata, lateralia 2—3 seriatim posita, rarius terminalia, ovato-oblonga, 8 — 10// longa et b—Q(i lata. Of this characteristic species I have only succeeded in finding a single specimen. It was growing upon a Cewiroceros-plant for- ming a small tuft. 60 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 63. Acrochætium ernothrix nov. spec. Erect ramified filament with sporangia-bearing branchlets ended with hairs. (About 150:1). As to the base I much regret that I have not been able to state with certainty how it is formed having only had a single specimen. By means of chlor- zinc jodine, which coloured the Acrochætium and at the same time had a clearing influence upon the tissue of the host plant, I have arrived at the conclusion that the base most probably consists of a few creeping filaments somewhat immersed in the tissue of the host plant. From this basal part an erect filament arises which im- mediately begins to give off bran- ches forming in this way a small tuft about 400// high. The prin- cipal filaments are rather straight (Fig. 63) ; they branch out in all directions along their whole length but mostly in the upper part. They consist of cells about 5 — 6// broad and 15 — 18// long. The chromatophore (Fig.64) is band- shaped often with more or less long prolongations along the wall of the cell; in the middle a large pyrenoid is pre- sent. The branches are of two kinds, short sporangia-bearing branchlets (Fig. 64) and ordinary branches growing out to filaments like the principal filaments and again branched in the same way. The branchlets have a very cha- racteristic appearance (Fig. 64). They consist of two or three, rarely more, cells the uppermost of which taper greatly and runs out in a long hair-like prolongation composed of two or three, Fig. 64. Acrochætium erno- thrix nov. spec. Branchlet with sporangia and hair. (About 350 : 1). F. Børgesen : Rhodophyceæ of the Danish W. Indies. 61 thin, nearly colourless cells. The whole length of the branchlet is about 80— 100 /y. The hair-hke prolongations have a length of about 50 fx and are about 1—2 fi thick in the summit. Upon the lowest cells of these branchlets we find a single or mostly two or three serially disposed sporangia (Figs. 63, 64). The lowermost sporangia are often pedicellate, the others sessile. Rarely sporangia are found terminally upon short two- or three- celled branchlets. The sporangia are ovate-oblong, 8 — 10 fi long and 5— 6/i broad. This species was gathered in a sheltered locality behind Long Reef at Lt. Princess, St. Croix. Subfam. 2. Nemalieæ. Nemalion Targioni Tozzetti. 1. Nemalion Schramm! (Grn.) Borgs, Borgesen, F., Some new or little known West Indian Florideæ, I (Botanisk Tidsskrift, vol. 30, 1909, p. 4, pi. 1). Helininthocladia Schvammi Crn. (nomen nudum) in Maze et Schramm, Algues de la Guadeloupe, 2e Edit., Basse-Terre 1870-7, p. 177. On the south side of St. Croix I have found some few but large and well developed specimens of a Nemalion which I in my above mentioned paper have referred to Helminthocladia Schrammt Crn. For details I refer to the above mentioned paper and shall here only give a description of the plant. The specimens when living had a very gelatinous surface so that they slipped out of one's hand like an eel; on the other hand the consistency was rather tough. The colour was a dark redbrown. The thicker main branches which reach a thickness of about l^/g cm were somewhat compressed, the thinner nearly terete. The surface was smooth in places, being somewhat curled or crisp especially in the thicker branches. On drying they adhere strongly to the paper and gradually take on a dirty, yellow-brown colour. The plant was fastened to stones and shells on the bottom by means of a small roundish disc at the base. The specimens are irregularly ramified on all sides, often too with numerous proliferations at the apices (cfr. 1. c. plate 1). 62 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The middle of the thallus consists of a tissue of colourless, rather poorly ramified, cell-threads which are loosely interwoven (Fig. 6b E); the cell-threads are from 2 to 12/z thick and con- sist of rather long and thick-walled cells. Towards the periphery these hyphæ-hke cell-threads are more richly ramified and here pass evenly into the radially pla- ced assimilating fila- ments, which are arran- ged in small groups (Fig. 65 A). They are dichotomously divided, moniliform, consisting of oval cells which are about 28// long and of about half that in breadth. In the upper end of the cell lies the chro- matophore, but often it fills up also more or less the whole cell; it is irregularly star-like, consisting of numerous strands which radiate from the centre of the cell in all directions (Fig. 65 F) ; when these strands meet each other at the periphery of the cell they grow together and form a clathrate layer with large and numerous openings with- in the cell -wall. In the central body of the chromatophore a pyre- noid is present which was densely stained by means of hæma- toxyline. The structure of the chromatophore seems thus to be in good agreement with that of Nemalion multifidum according to Wolfe's description ("Annals of Botany", vol. XVIII, 1904, p. 610) with the exception that he has not found a pyrenoid in his material. And further it also seems to agree well with that Fig. 65. Nemalion Schrammi {M. eiS.) Børgs. yl, assimilative filaments with two carpogonial branches lA, 140: 1). B and C, groups of car- pogonial branches. (B, 160 : 1, C, 140 : 1). D, cystocarp with decayed trichogyne (140 : 1). E, colourless cells from the middle of the thallus (140 : ] ). F, Two assimilative cells with chromatophore, pyrenoid and nucleus. (250: 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 63 of Nemalion luhriciim according to the statement of L. Kurssanow in "Flora", 99. Bd., 1909 p. 311. It is here pointed out in ac- cordance with the opinions of earher investigators and in con- tradiction to Wolfe's statement that a pyrenoid is present in the middle of the chromatophore. Rarely the vegetative cells terminate in a rather long hair (Fig. 65 A). Most often the main cell-thread in the middle of the above mentioned groups of assimilating-filaments terminate in a carpo- gonium and further also often 2 — 4 or more side-branches like- wise bear terminal carpogonia (Fig. 65 A). Fig. 65 C shows a branch dichotomously divided, in which the branches terminate in a carpogonium. The carpogonial branch is composed usually of 4 cells, but sometimes only 3 occur, occasionally even 5. This is in agreement with Nemalion miiltifidum where the number of cells also is some- what variable. Bornet and Thuret^) give the number to be 3 — 4, Janczewski^) indicates it to be composed of 3 cells and Wolfe (1. c, p. 613) writes: "This carpogonic branch is composed usually of three cells; since, however, the number varies from two, in the simplest noted, to as many as five, it cannot be considered as in any way significant". A well developed nucleus was found in each of the cells of the carpogonial branch (Fig. 6b B); on the other hand the chromatophore was not very conspicuous even if it was not quite absent as Janczewski describes it. The cells of the carpogonial branch are roundish-subquadrangular and usually a little shorter and thicker than the vegetative cells in the lowest part of the cell-thread. By means of this they are also most often easily recognisable though I must confess that it may sometimes be difficult to decide where the carpogonial branch begins and the vegetative cells end, as Wolfe has also pointed out in this way concerning the carpogonial branch of Nemalion miiltifidum (1. c. p. 613): "The lowest cell of the series partakes to some extent of the characters of both, and thus lessens the abruptness of the transition between the two types". The carpogonium bears a rather short and often somewhat bent trichogyne which is swollen towards its apex. In spite of ^) Bornet, E. et G. Tu uret, Recherches sur la fécondation des Floridées (Ann. se. nat. Botanique, V. sér., t. 7, 1667 p. 141). *) Janczewski, E., Notes sur le développement du cystocarpe dans les Floridées. (Mém. de la Soc. Nat. d. Se. Nat. de Cherbourg, vol. XX, p. 109). 64 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. much search I have not succeeded in finding antheridia; occasionally some decayed fragments of what perhaps might be remains of anthe- ridia were found at the tips of the filaments, but it seems to me very doubtful what they really were. Most probably the specimens are dioecious in accordance with what Rosenvinge (1. c. p. 146) has stated to be commonly thecase with Nemalion midtifidum in the Danish waters. I have never seen spermatia in contact with the trichogyne. Nearly all the material at hand was found in this stage of development. In the youngest tips of the plant only were no carpogonial branches yet developed. After much search and by taking samples in different parts of the dried material I have however found a few cystocarps of which fig. 65 D illustrates one. If these are normally constructed, the sporogenous filaments seem to be more loosely connected than those in Nemalion miiltifidum. The carpospores are about 11/^ broad. This species was found in shallow water fixed to stones and shells near the shore. The locality was rather sheltered; but nevertheless small waves occur by which the plant was moved to and fro. Only collected once in the month of February on the south coast of St. Croix: at Long Point. Geogr. Distrib.: West Indies. 2. Nemalion longicolle Borgs. Borgesen, F., Some new or little known West Indian Florideæ, I. (Botanisk Tidsskrift vol. 30, 1909, p. 8, pi. 2). This species was growing together with the preceding one which it very much resembled in colour and outer habit. For this reason I did not observe when collecting the plant that it was different from N. Schrammt and I have therefore unfortun- ately not preserved it in any other form than dried. It was only during the microscopical examination here in Copenhagen that it became clear that my material contained two forms and after having arranged them in accordance with the different microscopical characters they then showed quite plainly a difference in habit also. Thus the specimens (1. c, plate 2) when compared with N. Schrammt were found to be more slender, the thickest branches being 5 — 7 mm thick. They were richly subdichotomously or laterally ramified and the thallus had not the crisp folded sur- face to be found in N. Schrammt. The colour of the dried spec- F. Borgesen : Rhodophyceæ of the Danish W. Indies. 65 imens was red-brown in contrast to the more dirty yellow-brown in N. Schrammt. As to the anatomical structure, this species consists in the interior of nearly colourless, long-celled, hyphæ-like, thick- walled cells running mostly in a vertical direction, interwoven and from 3 — 14 ;M thick. Near the periphery they are more richly ramified and bear here the horizontal assimilating filaments which radiate outwards in small bundles and branch dichotomously (Fig. 66 A). Innermost at the transition from the medullary tissue the cells are rather long and nearly cylindrical but they grow soon shorter and at the same time become swollen in the middle in such a way that the cell-threads be- come moniliform, reaching a thickness of about 13 — 14;/. Compared with N. Schrammt the cells are somewhat slender. The chromatophore (Fig. 66 C) is stellate and resembles very much that of N. Schrammt though as a general rule it only fills half the cell ; of the outer- most ones nearest to the periphery it occurs at the top, while it is found in about the middle of the slender and more cylin- drical cells further in. In the middle of the chromatophore a pyrenoid is present. Having only dried material for examination I have not succeeded in finding the nucleus. In the middle of each of the peripheral bundles of assimil- ating filaments a single cystocarp occurs (Fig. 66 A, B); it is very rarely that a second one develops on a side-branch. While in N. Schrammt nearly all the material was in the stage of development mentioned above, viz. with the trichogynes still present, in Nemalton longtcolle nearly all the material had ripe cystocarps. These are terminally placed on a rather long straight branch, the cells of which are shorter and nearly cylindrical, Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1915). 6 Fig. ßß. Nemalionlongicolle Børgs. .4, bundle of assimilative filaments in the middle of which the cystocarp (140:1). B, another cystocarp (140:1). C, cells with chroma- tophore and pyrenoid (250: 1). D, carpo- gonial branch with trichogyne (140: 1). 66 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. grading rather evenly over into the cells belonging to the carpo- gonial branch ; sometimes also as shown in fig. 66 A the growth of the branch has stopped and a side-branch has then grown out as a prolongation of the mother-branch bearing the cystocarp. The carpogonial branch is composed of 4 — 6 cells; these are shorter than the vegetative ones and contain only a slightly developed inconspicuous chromatophore or only remains of it. The cell- walls of the carpogonial branch are distinctly stained by hæma- toxyline. The cells in the carpogonial branch are about 9 ju thick. In the youngest tips of the plant some younger carpogonial branches occurred and a few with trichogynes still preserved were found in the older part of the thallus perhaps because they had not been fertilized ; the trichogyne had nearly the same form as in N. Schrammi, growing thicker towards the tip (Fig. 66 D). The carpospores were about 14// long and 11// broad. As to the outer habit, I may add that near the base the thallus grows at first thinner but finally it broadens out again to a small disc, by means of which the plant is fastened to stones and shells on the bottom. The plant was growing in shallow water quite near the shore in rather sheltered localities where it swings to and fro following the feeble motion of the sea. It was collected in the middle of February having at that time ripe or nearly ripe cystocarps. Only found once on the southern coast of St. Croix: at Long Point. Liagora Lamour. As is well known J. Agardh has given a survey of the anatomical structure of the species of Liagora. The title of his paper is: "De differentiis in structura frondis, quæ in diversis Liagoræ speciebus observantur" (in "Analecta Algologica", Conti- nuatio III, Lund 1896, p. 96). This paper does not seem to be quite satisfactory most probably because J. Agardh had not sufficient material and has based his description exclusively upon dried material. Several of his species seem to be so closely related that they most probably belong to one another being forms of the same species. In any case it is not always an easy task to determine by means of J. Agardh's description a Liagora-spec- imen. A monograph of this genus would certainly be of much use. Zeh^) has promised such a work, but up till now he has merely ^) Zeh, W., Neue Arten der Gattung Liagora (Notizblatt des Königl. bo- tanischen Gartens und Museums zu Berlin. Band V, 1913, p. 268). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 67 given short diagnoses of some new species, which has only added to the difficulties. Having now examined my West Indian ma- terial of this genus I have found that good characters are pre- sent not only in the shape of the assimilating filaments but also in that of the carpogonial branch, of the antheridia and the cysto^ carps. In the last mentioned, especially, the filaments surrounding the sporogenous filaments are very differently developed. In the specimens which are not easily recognizable by means of the external habit, e. g. rami- fication, calcification etc., these characters of internal structure might be of great assistance. Judging from the de- scription of Butters ^) Lia- gora reminds one much of Trichogloea, the essential difference is that the carpo- gonial branch is lateral in Liagora, and terminal in Trichogloea. 1. Liagora elongata Zanard. Zanardini, G., in Flora, vol. 34, 1851, p. 35; Plant, in Mari Rubro . . . (Memoria Isti- tuto Veneto, vol. VII, 1857, p. 274, tab. 6, fig. 1). Kützing, F., Tabulæ Phycol., vol. VIII, 18,58, pi. 94 II. Agardh, J., Epicrisis, p. 516; AnalectaAlgo- logica, Contin. Ill, p. 105. Fig. 67. Liagora elongata Zanard. Part of a plant. (About 3:1). As pointed out by J. Agardh (1. c. p. 105) this species is characterized by the fact that the cells in the robust assimilating filaments (Figs. 68, 69 a) have nearly the same breadth through their whole length and further that the cells are seldom longer than double their diameter. The assimilating filaments are not much ramified ; the branches arise mostly at an acute angle from the mother filaments and are all straight or nearly so. *) Butters, Fr. K., Observations on Trichogloea lubrica. (Minnesota Bo- tanical Studies, Third Series, Part I, 1903, p. 11). 5* 68 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The lowermost cells in the assimilating filaments are larger and often somewhat irregularly shaped ; their breadth is about 40//; higher up the cells grow thinner, about 11 /j. and keep this diameter almost until the apex. The whole assimilating fdament reaches a length of about 400 — 500/^. The medullary cells are large subcylindric-barrelshaped, their diameter reaching a length of up to IbOju or more and the whole length of the cells about ten times the breadth. With a trans- Fig. 68. Liagora elongata Zanardini. a, assimilating filaments with liairs and (b) with antheridia. (a, about 140 : 1, b 60 : 1). verse section (Fig. 70) one sees that they are not lying close to- gether in any case not after decalcification, but imbedded in mucilage, and in this irregularly bent thin filaments run in all directions ; these last mentioned filaments consist of long nearly cylindrical cells, the diameter of which is about 8 — 10 fj. and their length about 10 times the breadth. These thin filaments have their origin from the large basal cells in the assimilating fila- ments. From nearly all the summits of the young assimilating fila- ments long hairs arise (Fig. 68); these are about bfi thick, in their uppermost somewhat swollen end about 8/u. and reach a F. Borgesen: Rhodophyceæ of the Danish W. Indies. 69 length of about 250//. They are quite hyahne with the excep- tion of the uppermost end which is almost entirely filled with protoplasm. The calcareous layer is rather thick, but uneven and loose ; it extends from the medullary tissue to about the upper third part of the assimilating filaments which are free and protrude freely together with the antheridia and hairs found here. The antheridia (Fig. 69) are found on the summit of the assimilative filaments and form dense hemispheri- cal or pyramidal clusters. The development of the antheridia takes place as fol- lows (Fig. 69) : The end of an assimilating filament which is at the same time rich on contents is prolongated coni- cally and divided by trans- verse walls into several small cells ; from these again Fig. 69. Liagora elongata Zanard. a, me- dullary cell with assimilating filaments and antheridia. b and c, development of antheridia; d, e, nearly ripe antheridia, e, in transverse section, (a, about 60 : 1, b. c, d, e about 300 : 1). small conical outgrowths arise on all sides which soon are divided by transverse walls (Figs. 69 b, c) giving rise to small branches. These are repeatedly di — trichotomously branched into several small branchlets, the end cells of which are the antheridia (Fig. 69 e). In the material collected I have only found antheridial plants ; so I cannot give any information as to the carpogonial branch or cystocarp. Forms of this species have been fre- quently referred to the Australian plant Liagora Cheyneana Harv., a species which also shows not a little likeness to Liagora elongata. Fig. 70. Liagora elon- gata Zanard. Trans- verse section of me- dullary tissue. (About 60:1). 70 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. This species has been found in the month of February near the shore in shallow water in a somewhat exposed place. St, Croix: Long Point. Geogr. Distrib. : Red Sea, Mauritius, Florida, West Indies. 2. Liagora corymbosa J. Ag. Agardh, J., Analecta Algologica, Contin. Ill, 1896, p. 104. Of this plant I have had only a single dried specimen at my disposal. This specimen agrees well with the few found in J. Agardh's Herbarium at Lund. The plant has a rather characteristic appearance ; it is reddish brown when dry and has a very scabrous surface which examined under a lens is found to be composed of dark red and whitish dots. The ramification is irregularly dichotomous with numerous prolifications, the branches spreading out at nearly right angles. Having had only dried material I shall not enter upon a more detailed description of the anatomical structure but only point out that it seems to agree closely with that of L. elongata. The cells in the assimilating filaments are nearly cylindrical or a little barrel shaped, about 2 — 3 times as long as broad and about 11 H thick. The antheridia also seem to agree exactly with those of L. elongata. Most probably therefore this species is only a variety of that plant. Zeh, who has had the material in the Botanical Museum, Copenhagen, for determination, has named the specimens of this alga as L. elongata. This plant has only been collected as washed ashore material and was sent to me by Dr. Hamburger. St. Croix: Sandy Point. Geogr. Distrib.: Florida, Bermudas. 3. Liagora valida Harv. Harvey, W. H., Nereis Bor.-Am., Part II, 1853, p. 138, tab. 31, A. Agardh, J., Epicrisis, p. 517; Analecta algologica, Contin. Ill, p. 107. KüTZiNG, F., Tab. Phycolog., vol. VIII, pi. 92 I. This species was originally described on specimens from Florida, and judging from Harvey's clear description my spec- imens seem to agree well with them. The plant is characterised by having a terete frond (about 1 mm thick) which is fairly regularly dichotomous. The calcareous coating is quite continuous giving the plant an even surface and when dry a whitish colour ; F. Børgesen : Rhodophyceæ of the Danish W. Indies. 71 only in the summits of the frond is it not so complete allowing the red-brown tips of the assimilating filaments to protrude. Also the cystocarps project above the calcareous layer and are seen in the fruiting specimens as dark red dots (comp. fig. 71). The assimilating filaments have, as pointed out by J. Agardh, a corymbiform outhne (Fig. 72). They reach a length of about 200 /^ or somewhat more. They are 4 — 5 times repea- tedly forked. The uppermost cells are pearshaped or broad oval, about 10 — 12// thick (Fig. 73 b) ; lower down in the filaments the cells grow longer, at length becoming subcylindric. The lowermost cells are about 16 // thick. The central filaments consist of subcylindric cells somewhat tapering towards the ends (comp. figs. 72 and 74 a) ; they are about 20 — 40/^ thick or more, and often reach a length up to 20 times their own diameter. They have very thick walls. Between these thicker filaments run thinner ones (lat, about 8//), as the transverse section of the medullary tissue shows (Fig. 74): These thin filaments originate from the lower- most cells in the assimila- ting filaments (comp. fig. 75 a). They run between or creep along the medul- lary filaments ; and from those near the surface erect filaments arise (comp. fig. 73 a). They are somewhat branched and consist of oval cells ; they grow up between the assimilating filaments. As they have well developed chromatophores they may be considered as a kind of secondary assimilating filaments. The carpogonial branch is borne upon one of the cells in the Fig. 71. Liagora valida Harv. Part of a plant. (About 3:1). Fig. 72. Liagora valida Harv. Assimilating filaments with carpogonial branches. (About 60 : 1). 72 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. middle of the assimilating filaments (Fig. 72). Besides the car- pogonial cell with the trichogyne it consists most commonly of 4 cells (Fig. 75 b), sometimes of 3 only. The branch is compara- tively thick, the diameter reaching often a length of 22//. After fecundation the carpogonial cell is divided by a transverse wall into two cells from the uppermost of which the sporogenous fila- ments grow out (Fig. 75 a), while the lowest remain undivided. The cystocarp (Fig. 75 c) is a comparatively large spherical body which reaches often more than 400,« in diameter. It consists of thin sporo- genous filaments (lat. about Sju); these are ramified, more or less woven together and composed of rather long nearly subcylindrical or more irregularly shaped cells. At the end of the filaments the carpospores are produced (Figs. 75 d, e) ; these reach a length of about 10 /u while their diameter is about 5—6//, After the fertilization of the carpogonium several ramified filaments arise from the cell below that upon which the carpogonial filament is inserted. These pericarpic filaments consist of thicker, oval, often nearly spherical, sometimes also more irregularly shaped cells ; they grow up- wards around the cystocarp. Furthermore from the basal part of these cells and also from the sporogenous filaments thin hair-like filaments grow downwards often in great numbers (Fig. 75 c). The antheridia I have not found in my material; on the other hand they were present abundantly in a specimen from Key West, (Farlow, Andersson & Eaton, Alg. Am. Bor. exsicc, no. 70) in Herb. J. Agardh in Lund. The antheridia are found on the summits of the assimilating filaments whose uppermost cells are divided into thin filaments in the end cells of which the spermatia are developed. Fig. 73. Liagora valida Harv. a, assimila- ting filament (comp, the text), b, Part of a filament showing shape of the cells, (a, about 60:1; b, about 160: 1). <.%'L'' ® Fig. 74. Liagora va- lida Harv. Trans- verse section of the medullary tissue. (About 60: 1). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 73 Liagora tenuis J. Ag. seems to come very near to this species judging from the few specimens upon which J. Agaedh based his description. Compared with L. valida the thallus seems to be a httle thinner, but except for this not very essential diffe- rence they are very ahke. Of one of the specimens, collected at Florida by Miss Curtiss a small piece was examined; it had the assimilating filaments less rami- fied than in L. va- lida and the fila- ments had not the corymbiform out- line, but to decide how far these dif- ferences are other than casual de- velopment much more material is necessary. Liagora annii- lata J. Ag. also seems to come near to Liagora valida ; ' / h indeed, most pro- Y\g. 75. Liagora valida Harv. a, assimilating fila- bablv it is only ment with young cystocarp, b, carpogonial branch, . . f .u-" c, cystocarp with surrounding filaments, f/, e, sporo- a variety Oi tnis ggnous filaments with carpospores. [a and c about species; asuppo- 60 : 1; fc, f/, 160: l; c, 140: l ; e, 250: l). sition I have con- firmed by the fact that in some of my specimens now and then a rudimentary annulation is present. But to settle this question rich material is necessary. In his paper, "Notes on Bahaman Algæ^)", Howe considers it as a distinct species. Liagora valida has been collected with ripe carpospores in January and February. It grows in shallow water in the upper sublittoral region and in somewhat sheltered places. St. Croix: At White Bay near tlie south west end of the island and at Coakley Bay upon the north side. Geogr. Distrib.: West Indies, Madagascar. 1) Bulletin of the Torrey Bot. Club, vol. 31, 1904, p. 99. 74 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 4. Liagora pinnata Harv. Harvey, W. H., Nereis Bor.-Americana, part II, 1853, pag. 138. Agardh, J., Epicrisis, 1876, pag. 517; Analecta Algologica, Contin. III, 1896, p. 108. The piants (Fig. 76) I have referred to this species seem to accord well with the description and figures of Harvey (1. c.) even if they show some differences. Harvey describes the frond as three inches long ; my specimens reach a length of up to 16 cm. The stems are set at short intervals with branches, spreading out on all sides longest in the middle of the frond, shorter upwards and down- wards. These branches bear again branch- lets placed in the same manner and the branchlets again ramuli. Harvey says Fig. 76. Liagom pinnata ^-j^^^^ ^j^g ramuli are "often opposite" but Harv. Part of a plant. , . , .,, ^ (About 3 : 1). this does not agree with my observations. For the rest I refer to Harvey's good description of the dried plant ; his comparison of the very uneven surface with "pepper and salt" is very strik- ing , darker red- brown dots protru- ding over the whitish coating originating from the upper end of the assimilating filaments and cysto- carps. The central nearly or quite colourless filaments in the thal- lus consist of long more or less cylin- drical cells tapering usually somewhat near their ends (Fig. 77 a) ; these cells are about bOju thick and about 8 times their own length; but some Fig. 77. Liagora pinnata Harv. a, assimilating filament w^ith carpogonium and antheridia, b, part of an assimilating filament with antheridia (a, about 60: 1; b, 160:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 75 occur which reach more than 100 ii in diameter ; besides these cells there are many of a much more irregular form. The assimilating filaments (Fig. 75 a) consist at their base of nearly cylindric cells about 40 /i thick and 2 — 3 times as long as broad. The filaments branch several times (4 — 5 or more) the cells at the same time becoming gradually thinner, the thinnest being found somewhat over the middle of each cluster of filaments ; then they grow thicker again until near the top where they suddenly narrow conically. In the cluster of filaments represented in fig. 77 a the cell at the base is 40/i thick, the thinnest cells in the middle of the cluster are 11// and the thickest near the top 25/«. Fig. 78. Liagora pin- na?a Harv. Transverse section of medullary layer. (About 60: 1). Fig. 79. Liagora pinnata Harv. a, carpogonial branch, b, c, d, development of the cystocarp, (a and b, about 160: 1, c and (/ 150: 1). From the basal cell, and sometimes also from other of the lower cells in the cluster of assimilating filaments, rhizoidal fila- ments grow out along the central large filaments (77 a). These rhizoidal filaments consist of long more or less cylindrical or some- what inflated cells ; from these erect filaments grow up the cells of which are shorter but often rather thick, oval or rather irregularly inflated, the filaments in this way getting a somewhat moniliform appearance ; these filaments become intermingled be- tween the assimilating filaments of the periphery. Somew^hat below the middle in the cluster of the assimilating filaments we find the carpogonial branch (Fig. 77 a). This is placed laterally upon one of the cylindrical cells found here, and 76 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. is as a rule composed of four cells : three cells and the carpo- gonium with a rather long thin trichogyne (Fig. 77 a). After fertilization the carpogonium is divided by a transverse wall into a basal cell, which as is the case in Nemalion and Hel- minthora, remains undivided, and an upper cell. This cell is firstly divided by a more or less vertical wall into two cells, after which variously orientated walls arise (Fig. 79 b, c, d), the Fig. 80. Liagora pinnata Harv. Cystocarps, a, with sur- rounding filaments, b, showing carpospores. [a, about 60:1, b, 150:1.) result of which is a cluster of irregularly bent, ramified filaments (Fig. 80 a). These are the sporogenous filaments whose cells at the end of the filaments produce the carpospores (Fig. 80 &). When ripe these are oval or obovate, about 15 /i broad and 18« long. As a secondary result of fertilization sterile filaments begin to grow out from the cell immediately below the cell in the assi- milating branch upon which the carpogonial branch is found. These filaments grow up round the cystocarp forming a kind of co- vering about it but only very loose and im- perfect (Fig. 80 a). The antheridia (Fig. 81) are found in the same plant as the carpogonial branch and often in the same assimilating filament (Fig. 77 a). They are placed at the summit of short branchlets grow- ing out from one of the cells somewhat below the top of the assimilating filaments (Fig. 77 h). From the upper end of these branchlets ramified filaments, consisting of rather short cells grow out forming dense, nearly hemispherical clusters. The terminal Fig. 81. Liagora pin- nata Harv. Antheri- dia. (About 170:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 77 cells of these branchlets are the mother-cell of the spermatia. The cells have a rather thick wall and are when ripe about 3 — 4// in diameter. This species was found in rather exposed localities down to a depth of about ten meters, It was collected in the months January and February and was in a fructifying condition. St. Croix: White Bay, and near Buck Island in a depht of about 5 fathoms. Geogr. Distrib. : Florida, West-Indies. 5. Liagora megagyna nov. spec. Frons cæspitosa, 12 — 14 cm alta, teres, e basi sensim vix attenuata, irregulariter ramosa, ramis inferioribus longioribus, su- perioribus brevibus ramulos parvos obtusos irregulariter dispositos gerentibus. Crusta calcarea in specimine exsiccata farinaceo-scabrida. Axis centralis ex filamentis crassioribus cellulas subcylindrice- dolioformes continentibus et filamentis tenuioribus, compositus est. Stratum periphericum ex filamentis dichotomis, cellulas sub- cylindricas ad apicem ver- sum oblonge-ovales conti- nentibus compositum est. Rami carpogonii robusti, recti aut fere recti, ex 3 — 5 cellulis brevibus composite Cellula carpogonica brevi- ter conica in trichogynum longum cylindricum pro- ducta. Cystocarpia fere sphæ- rica ex filis carposporiferis composita, plus minus fila- mentis sterilibus, ex cellulis infra ramos carpogonii ortis, circumcincta. The ramification of this species is very irregular, sometimes apparently mono- podial, sometimes more or less dichotomous with many proliferations (Fig. 82). The frond is terete and the calcification well developed for- ming a continuous covering ; only at the summits of the branches Fig. 82. Liagora megagyna nov. spec. Part of a plant. (About 3: 1.) 78 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. is the calcification nearly wanting. The surface is glabrous, in dried specimens uneven or dotted. The fascicles of assimilating fila- ments (Fig. 83 a, 6, c) are propor- tionally large and richly ramified. The lowermost cells in each fascicle are large, somewhat swollen upwards, but very variable in size, their dia- meter often reach- ing a length of 40// or more. From these ba- sal cells 2 — 3 or more filaments grow upwards ; these are several times di- or tricho- tomously divided. The lowermost cells in these filaments are subcylindrical or nearly so ; after each division the cells grow thinner and also shorter until about the middle of the whole branch system where the cells on an average are only 10—15 It thick. From here the cells again get thicker and at the same time also shorter, nearly oval, the ends of the assimilating filaments in this way getting a monihform appearance. The cells in the upper part of the assimilating fila- Fig. 83. Liagora megagyna nov. spec, a, &, c, d, assimilating filaments with carpogonial branches and hair-like filaments, e, ends of assimilating filaments with remnants of died cells, f, g, end of assimilating filaments with short hairs, (a, b, d, about 60: 1, c, e, f, g, about IBO : 1.) F. Børgesen: Rhodophyceæ of the Danish W. Indies. 79 Fig. 84. Liagora rnega- gyna nov. spec. Transverse section of medullary layer. (About 60:]). merits are about 19 — 20// thick and 30 — 35 ^u long. The whole fascicle reaches a length of up to 500 — 600//. Peculiar hairlike organs arise everywhere in the filaments (comp. Fig. 83 a, c, d). These are short, con- sisting of a single cell only, or longer, some- times ramified, and composed of cyhndrical cells whose diameter is 5 — 8«. The upper- most cells in these filaments are almost en- tirely filled with protoplasm ; whatever the reason may be the whole contents are often evacuated from the cells and found mostly as a spherical but sometimes also more irre- gularly shaped body at the end of the fila- ments (Fig. 83 c). Something quite similar often takes place also in the cells at the summit of the assimi- lating filaments ; here also now and then the whole contents of the cells are emptied through a hole in the top of the cell ; remnants of a membrane originating from such emp- tied cells are often found in the end of the assimila- ting filaments (Fig. 83 e). Here also short hairs are often found (Fig. 83 /, g), reminding one of those which RosENViNGE has found in Nemalion. They are entirely filled with protoplasm ; when they die remnants of the walls remain at the end of the cell. The central filaments consist of long subcylindrical barrelshaped cells, whose . .^. .... Liagora niegagyna nov. spec. diameter reaches a length Development of the cystocarp (comp. of 100 — 160// or even more the text), (a, bM 160 : 1, c about ^^^^p_ ^^^ g3 ^^ ^^y ^j^^^g and between these thicker filaments smaller ones run irregularly in the mucilage ; they ori- ginate from the basal cell in the peripheral filaments and consist of long cylindric cells about 150/« long and 11// broad. Fig. 84 shows a transverse section of the medullary layer. Fig. 85 80 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. In about the middle of the assimilating filaments vigo- rous carpogonial branches are found (Fig. 83 a, b, c) ; these are nearly straight and placed laterally near the upper end of the almost cylindrical cells found here. Besides the carpogonial cell with its long trichogyne, it consists of three or four, rarely five cells. These have rather thick walls, are mostly shorter than long and a little swollen in the middle ; their diameter reaches a length of about 20—27;/, The shape of the carpogonial cell is short conical ; it has rather thick peripheral walls. The full grown trichogyne is nearly cy- lindrical, often somewhat irre- gularly bent towards the sum- mit, and a little thicker here; when young it is seen as a short obovate outgrowth from the carpogonial cell, later, on gradually growing longer, it assumes a clavate appearance and becomes at last nearly cylindrical. Having only found a very few fertihzed carpogonia show- ing later stages I have not been able to follow the development in more detail. The youngest stage found is shown in fig. 85 a ; we see here the outgrowth of the sporogenous filaments. Fig. 85 b shows a more advanced phase and in fig. 85 c is portrayed a nearly ripe cystocarpium. As is the case in other species so here the fertihzation of the carpogonium exerts an influence upon the cell from which the carpogonial branch is issued and also upon some of the neigh- bouring cells; from these numerous filaments grow out more or less surrounding the basal part of the cystocarp. Vegetative filaments were found several times in this species growing out from not fertihzed carpogonial branches. Such out- growths were either lateral from the cell below the carpogonium (Fig. 86 c) or terminal from the carpogonium itself (Fig. 86 d). In this species I have not succeeded in finding antheridia. Tliis plant has only been found once in shallow water at Long Point at the south coast of St. Croix. 6. Liagora pulverulenta C. Ag. Agardh, C, Species Algarum, 1821—2, p. 396. Agardh, J., Epicrisis, 1876, p. 516; Analecta Algologica, Continuatio III, 1896, p. 101. Fig. 86. Liagora megagyna nov. spec. a, b, development of the trichogyne. c, d, carpogonial branches producing vegetative filaments, (a, b, d, about 160 : 1, c, 60 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 81 a Fig. 87. Liagora pulverulenla C. Ag. Parts of two specimens from Rust up Twist. (About 3:1). The specimens I have referred to this species have a more or less re- gular dichotomous ramification but at the same time a good many proli- ferations are pre- sent (Fig. 87). The assimila- ting filaments (Fig. 88 a, b, c) are re- latively short, about 300 fx long; they are 5 — 6 times forked and their outline is corymbi- form. In the lower part bf the filaments the cells are subcylin- drical, about 9 — 12 ju thick; higher up they become very thin their diameter varying from 3 — 6 fj. ; to- wards the summits of the filaments they rather sud- denly grow shorter and at the same time thicker, oval or in the uppermost part nearly spherical, their diameter reaching a length of up to 12 ju. The cells in the summits of the young assimilating filaments often have long thin hyaline hairs whose length sometimes reaches double that of the assimilating filaments. When young these hairs are clavate with much pro- toplasm especially in the thickened end (Fig. 88 d, e, /) ; later they become 6 80Ta: Fig. 88. Liagora pulverulenla C. Ag. a, assimilating filament, b, part of the same with a hair, c, assimilating filament with carpogonial branches, d, e, f, young hairs. {a, about 140 : 1 ; b, 200 : 1; c, 60 : 1; (/, e, f, 160:1). Dansk Botanisk Arkiv, Bd. 3. Nr. 1. (191C). 82 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 89. Liagora pul- verulenta C. Ag. Trans- verse section of me- dullarv tissue. (About ^ 60:1). elongated and cylindrical with very little parietal protoplasm. From the lowermost cells in the assimi- lating filaments some thin filaments arise (Fig. 88 c) running along and between the central filaments ; they are branched and consist of rather long nearly cylindrical cells whose diameter is about 11 [i. From these erect filaments with oval cells occasionally grow upwards between the assimilating fila- ments (comp. Fig. 92 a). The filaments of the medullary tissue are subcylindric-barrel- shaped ; their diameter reaches a length of about 100;^ or more; in the mucilage be- tween these large filaments run many thin ones ; Fig. 89 shows a transverse section of the me- dullary tissue in which the large cells and the thin fila- ments are seen, in their respective pos- itions. The carpogonial branch is found nearly in the middle of the assimilating filaments (Fig. 88 c). It is placed laterally upon one of the near- ly cylindrical cells found here. It con- sists of three cells and the carpogonium with the triohogyne. It is characterized by being much cur- ved, the outline of the whole branch forming nearly a semicircle and its cells seen from the side having nearly a triangular shape ; their diameter Fig. 90. Liagora pulverulenta C. Ag. Development of the cystocarp. [a, b about 160:1; c, 150 :1; d 140 : 1). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 83 reaches a length of about 12 — 14;/. The carpogonium is conical and passes evenly into the long trichogyne. After the fertilization (comp. Fig. 90) the sporogenous fila- ments grow out. These are repeatedly branched and form to- gether a spherical rather compact body. In the summit of the filaments the carpospores are developed. Apparently even before fertilization, or in any case before any visible cell division has taken place in the carpogonium, filaments begin to grow out from the cell underneath that upon which the carpogonial branch is placed and these filaments are often considerably developed before the division of the carpogonium has begun (Fig. 90 a, h). In the more developed carpogonium they grow longer being several times forked and bent inward and they more or less surround the young cystocarp (Fig. 90 c); in the mature cystocarp on the other hand they are present like a whirl of prominent filaments at its base, and have the appear- ance of a collar thus giving the cystocarp a very characteristic aspect (Fig. 90 d). The antheridia are developed in the ends of the assimilating filaments as quite small oblong cells ; they are 2 — 3 fj. thick. In the material at hand they were only present in very small numbers. I have not found an- theridia and cystocarps together in the same plant. The above description is based upon material in spirit sent to me by Mr. 0. Hansen Ganneskov and collectod at Rust up Twist on the north side of St. Croix. Other specimens which I also refer to this species show a few differences. They w^ere gathered in Lime Tree Bay on the south side of the same island where I found them growing epi- phytic upon Udotea flabellata in shallow water. Fig. 91 shows that the plant was a little more robust than the first described and the proliferations more regularly forked. The assimilating filaments (Fig. 92 h, c) had nearly the same size and shape, but the uppermost cells in the filaments were more sphe- rical often nearly globular. The few carpogonial branches (Fig. 92 d) found were curved in the same way, but they contained only two cells besides the carpogonium which was very long. Neither more developed carpogonia nor cystocarps were present in the plant. 6* Fig. 91. Liagora pul- verulenta C. Ag. Part of a plant. (About 3:1). 84 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Some few other dried specimens I have also with some doubt referred to this species; but having had only dried and scanty material I shall not enter upon a description of them. In this connection I also want to point out that it is possible that some of these belong to L. leprosa J. Ag. How far this species is anything else than a form of L. pulverulenta I am not able to Fig 92 Liagora pulverulenta C. Ag. From Lime Tree Bay. a, basal part of assimilating filament (comp. the text, p. 82). h, assimilatmg filament. c assimilating filaments ended with long hairs, d, part of assimilating fila- ' ment with carpogonial branch, e, antheridia. (a. c, d, about 140 : 1 ; 6, GO: 1; e, 170:1.) decide. I am strongly inclined to think that the anatomical dif- ferences between the two species mentioned by J. Agardh, are merely accidental. During a visit to Lund I had opportunity to examine the specimens in J. Agardh's Herbarium and have not been able to confirm his observations. In a paper: "Notes on the species of Liagora and Galaxaura of central Pacific" Butters has F. Børgesen: Rhodophyceæ of the Danish W. Indies. 85 given descriptions of the two species in question but I do not think he has found any more exact characters by means of which the two species could be separated. The form of the carpogoniai branches he does not mention and a figure of the cystocarps would have been very desirable. This species occurs both in sheltered and in more exposed places. It has been found as an epiphyte upon Udotea flabellata but it is attached mostly to stones, shells etc. It occurs in shal- low water mostly ; once I have taken it in a depth of about 20 meters. It has been found at St. Croix: Lime Tree Bay, Rust up Twist; St. Jan: off Cruz Bay. Geogr. Distrib.: West Indies, Gulf of Mexico. Fani. 2. Chætangiaceæ. Subfam. 1. Scinaieæ. Scinaia Bivona. 1. Scinaia complanata (F. S. Collins) Cotton. Cotton, A. D., New or Uttle-known marine Algæ from the East (Kew Bulletin, 1907, p. 260) ex parte. Setchell. W. A., The Scinaia Assemblage (University of California Publications, vol. 6, no. 5, 1914, p. 100). Scinaia furcellata var. complanata Collins, in Phyc. Bor. Am-, Fasc. 17, no. 836, 1901; Rhodora, vol. 8, p. 110, 1906. Scinaia furcellata Harvey, Nereis Bor. Am., part 2, p. 136 (ex parte). var. intermedia n. var. A var. typica præcipue differt fronde angustiore cylindrica, axi centrali conspicua. In several respects the specimens found show very essential dif- ferences from Setchell's description, 1. c, that I have no hesitation in considering them as representing a new variety. The specimens (Fig. 93) reach a length of 8 cm. They all have a narrow frond the diameter of which reaches about 1 — 2 mm only, resembling as to this character the nartow specimens men- tioned by Setchell. As to the question whether these narrow specimens are flat- tened or not Setchell was not successful in solving the question with certainty only having dried material at his disposal. He writes: "While it is difficult to be absolutely certain whether the narrow forms are flattened or not, they seem to be so." I have 86 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. several specimens preserved in alcohol; when these are put in water they soon become turgescent and seem to assume quite the habit of the living plant. These specimens have shown themselves quite terete (Fig. 93). As far as I remember the living specimens were also terete. Normally the thallus is not constricted but in the lowermost older part of the plant narrowings are found rather often. These are, however, scarcely quite normal, it seems rather as if they ori- ginated from some kind of damage, parts of the thallus having been cut off and young thin filaments having grown up from the older and broader ones and in this way giving rise to the constrictions. As to the axial strand this was quite distinct through the whole thal- lus in the specimens preserved in spirit (Fig. 93), with the exception of the lowermost part quite near the base where the tissue of the plant is more compact and less translucent; in the dried specimens on the other hand it was not visible. It consists of about 20—30 broader filaments with propor- tionally tkick walls. The shape of the epidermal cells (compare Fig. 94) seems to agree exactly with the description of Setchell; they are flattened or a little convex at the upper (outer) end, closely packed, 3 — Ogonal in surface view, in section quadratic to flattened rect- angular, about 22 — 3Sju broad and 24—30// high. Below the epidermal cells the cells with chromatophores form together a very loose cell-layer most of the cells being quite free with large open intervals between them. To judge from Setchell's description and figures the cells in my plant seem to be more elongated pyriform than those in his plant (compare Fig. 94 a). The shape and the arrangement of the cystocarps appears to be in good accordance with the description of Setchell; the cystocarps occur scattered over the whole surface of the frond (Fig. 93) and are globular to pyriform in shape, narrowed abruptly Fig. 93. Scinaia complanata (Collins) Cotton, var. interme- dia nov. var. Part of a plant with cystocarps. (About 2: 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 87 outwards, about 200// long and 170// broad, but both larger and smaller ones occur. In a young growing tip Setchell found the '■''punctum vegetationis'''' convex projecting. As to this Setchell remarks: "Whether this is normal or not, it is strikingly different from the depressed punctum vegetationis as observed in all other species of Scinaia examined." In my specimens this is not the case; the tips of the plants in a turgescent state certainly appear to be convex projecting but when somewhat magnified the growing region is clearly found to be sunk. It can not be denied that these differences in my plants from the typical Scinaia complanata are very essential. Even if I left out of consideration the fact that in Setchell's plant the growing point is not sunk, which as pointed out by Setchell himself, is very probably not normal, the terete thallus in my plant is a very strik- ing character. And the axial strand being di- stinct through the whole thallus is of course also important and to these characters may yet be added the narrow thallus. On account of these differences we apear to be entitled to consider these narrow forms as a variety to which I propose the name intermedia, this variety appearing to me to be a connecting link between Scinaia complanata and Scinaia furcellata. In his newly published highly interesting paper on Sci- naia furcellata, Svedelius^) describes for the first time mono- spores as occurring in this species. As is well known tetraspores are never met with in Scinaia and the discovery of the mono- spores is therefore highly interesting. I have been looking care- fully for these organs in my specimens but without success, only antheridia were present. Also I did not succeed in finding Fig. 94. Scinaia complanata (Collins) Cotton, var. intermedia nov. var. a, part of the epi- dermal cell-layer seen from the inner side showing the arrangement of the assimilating cells, c, transverse section of the same tis- sue, b, epidermal cells and antheridia seen from above, [a and b about 250 : 1, c about 150:1). ^) SvEDELius, Nils, Zytologisch-entwicklungsgeschichtliche Studien über Scinaia furcellata. Ein Beitrag zur Frage der Reduktionsteilung der nicht tetrasporenbildenden Florideen. (Nova Acta Regiae Soc. Scient. Upsaliensis, Ser. IV, Vol. 4, No. 4. 1915). 88 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. hairs. The presence of hairs in Scinaia furcellata is mentioned by RosENViNGe^). These are now described in detail by Svedelius. This plant has been found in deep water only, in dephts from 20 — 30 meters. The specimens were collected in the month of March and had antheridia and cystocarps. It has been gathered in the sound between St. Thomas and St. Jan in several places of! Cruz Bay, and off America Hill in the sea to the north of St. Jan. Geogr. Distrib. Florida, Bermuda. Subfam. 2. Chætangieæ. Galaxaura Lamouroux. In his very valuable monographical work, "Om Floridé- slagtet Galaxaura, dess organografi och systematik" (Kongl. Svenska Vetensk.-Akad. Handl., Bd. 33, No. 1, Stockhlom 1900) Kjellman has shown that most of the older species are collective- species, in reality comprising often several easily distinguishable species. As a result of his examination Kjellman describes a great number of new species, he mentions in all 62, many of which seem to be very nearly related. As regards these species, how- ever, in all cases with which I am personally acquainted they seem to be well founded. These many species are relegated by Kjellman to nine principal groups, based essentially upon the different develop- ment of the assimilating tissue. Kjellman based his work exclusively upon material which was found in his own herbarium, and in Herb. Areschoug in Stockholm supplemented with specimens from J. Agardh in Lund. Without doubt this material has proved to be very rich as is evident from the numerous species it contained, but, never- theless, Kjellman's work would have been yet more valuable had he also cleared up, as far as possible, the older species and identified them with the forms which were found in the col- lections examined by him. This ought especially to be done with the species of Ellis and Solander described in "The natural history of many curious and uncommon Zoophytes", London 1786, a most valuable work for that time. 1) RosENviNGE, L. KoLDERUP, Remarks on the hyaline unicellular hairs of the Florideae. (Biologiske Arbejder tilegnede Eug. Warming paa hans 70 Aars Fødselsdag. København 1911, p. 204). F. Børgesen: R,hodophyceæ of the Danish W. Indies. 89 It seems, however, most probable that these old plants are no longer in existence. At my request Mr. A. D. Cotton has most kindly made a search in the Kew Herbarium without success and furthermore he writes to me that Mr. A. Gepp tells him that none of Ellis and Solander's types are in the British Museum and that he together with Mrs. Gepp had been to the Royal College of Surgeons, where the collection of Ellis and Solander was supposed to have been preserved and had made a personal search also without success. But of course this negative result is also of interest; had the species of Ellis and Solander existed an examination of these would certainly have resulted in several of the specific names of Kjellman being changed. By the fact that Liebman and Ørsted have sent Areschoug material of many of the algæ which they have collected in the West Indies, Kjellman has had relatively rich material from this region and several of his species are based upon specimens from the Danish Islands. During the determination of my col- lection it has been of great help to me to have had on loan all the material of Galaxaura determined by Kjellman. In the following survey 11 species are mentioned belonging to the following 5 of Kjellman's 9 groups, namely: Sectio I. Hhodara Kjellm. A. with long assimilating filaments .... 1. G. comans Kjellm. B. with long and short assimilating filaments. I. assimilating filaments often clearly arranged in belts 2. G. subverticillata Kjellm. II. assimilating filaments evenly distributed over the whole surface. a. thallus with long internodes, flagellate 3. G. flagellijormis Kjellm. b. thallus with shorter internodes 1. large, much ramified tufts, thallus flexible, densely covered with long hairs . 4. G. lapidescens (Sol.) Lamx. 2. low tufts, thallus fragile, rugose. 5. G. delabida Kjellm. Sectio II. Microtlioé Dcsne, J, Ag. a. thallus quite or nearly glabrous, annularly constricted internodes of nearly the same length 6. G. rugosa (Solander) Lamx. b. the assimilating filaments more persistent, less annularly constricted internodes of variable length. 7. G. squalida Kjellm, 90 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Sectio III. JEugalaxaura (Dcsne) Kjellm. a. With broader, proportionally shorter and somewhat rugose internodes 8. G. fragilis Lamk. b. With long, nearly eyhndric internodes 9. G. cylindrica Solander. Sectio IV. Brachycladia Sonder. 10. G. marginata (Sol.) Lamx. Sectio V. Vepreciilæ Kjellm. 11. G. occidentalis n. sp. Sectio I. Mhodura Kjellm. 1. (jalaxaura comans Kjellm. Kjellman, F. R., Floridé-slagtet Galaxaura, p. 44. This species Kjellman based upon a small, rather tiny but otherwise well developed specimen collected at Guadeloupe and sent to Areschoug from Crouan. The specimen (Fig. 95) I have gathered is large and vigorous, much larger than the original one, reaching a height of about 12 cm. It is irregularly ramified with long internodes of very vari- able length up to 3 cm or even more. The branches are very rigid and protuberant ; their diameter, including the hairs, reaches 3 — 5 mm being narrowed towards the apex. The whole thallus is densely covered with rigid prominent hairs and is of a dark red colour. A transverse section shows that the medullary tissue con- sists of proportionately thick filaments commonly about 20^ thick, but both thinner and thicker ones are present. The peri- pheral cells which bear the assimilating hairs are mostly almost isodiametric often quadrangular about 50 fi broad (Fig. 96 a) ; each cell commonly bearing a single assimilating filament, seldom two (Fig. 96 a). The assimilating filaments consist at their base of a large oval cell about 80 ^ long and 50 // broad ; then follow two or three still oval cells decreasing gradually in size. The rest of the filaments consists of cylindrical cells about 19// broad; the length of the cells is rather variable, some are up 40 // long or more, others especially in the upper end are shorter, not much longer than they are broad. The whole filament reaches a length of up to 1 — 2 mm. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 91 Kjellman found ramified fdaments rather frequently in his specimen and these occurred also in mine (Fig. 9Qb). '% £ ■iL ^- ^. ■f jr,,^^,fa., % ^ 'f /* 4 'j^^ "^m^ ^^' W %Mä -i: Fig. 95. Galaxaura comans Kjellm. Part of a plant. (About 1,5 : 1) This species has only been found once in a depth of 8 fathoms in the sea to the north of St. Jan: off America Hill. Geogr. Distrib. West Indies. 92 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 2. Galaxaura subverticillata Kjellm. Kjellman, F. R., Floridé-slagtet Galaxaura, p. 48. This species has been described from specimens which Ørsted col- lected at St. Croix and sent to Are- SCHOUG. In the Botanical Museum, Copenhagen, some more specimens of Ørsted's from St. Croix are to be found which quite agree with the specimens determined by Kjellman. The specimens I have collected (compare Fig. 97) seem to agree very well with the original examples. In this species both long and short assi- milating filaments are present and the most striking character is the verticillate arrangement of the fila- ments. This annular arrangement is most clearly present in the young parts of the thallus, in the older ones the long hairs occur in a more scattered manner over the whole sur- face and some specimens are even found in which the annular arrange- ment is much reduced, the specimens having an almost even but rather open covering of hairs over the whole sur- face. Kjellman explains this fact by considering that the short hairs later on grow out more or less into long ones. The surface of the thallus, espe- cially in that of the upper young ends, is rugose and often clearly annulated. The internodes are nearly cylin- drical, mostly constricted at the base, of variable length but usually short seldom exceeding 1 cm. The colour of my specimens was greyish olive-green with a reddish tinge especially in the younger parts of the thahus. A transverse section shows the medullary tissue to consist of the usual, rather thick walled, cylindric cells woven together. The Fig. 96. Galaxaura comans Kjellm. a, basal parts of as- similating filaments with the supporting cell, b, base of a ramified filament. (About 150 : 1). Fig. 97. Galaxaura suhver- ticillata Kjellm. Part of the thallus. (About 1,5 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 93 diameter of the central tissue being about 600 [x. The cells which bear the assimilating filaments are well developed, quadrangular (sometimes triangular), about 45 ^x broad. The short assimilating filaments usually consist of three some- times of two cells only. The basal cell is large, oval, about 65 ^ long and 45 fi broad. The diameter of the uppermost small cells varies between 16 and 25 fx. The sizes Kjellman gives for these cells are somewhat greater but in the specimen of the original material which I have examined I found the size of these cells agreeing very well with that of mine. In the long assimilating fila- ments the basal cells are of a similar size to those of the short filaments, the filament itself is about 16/^ thick and consists of cy- hndric thick-walled cells about 30 /i long. This species was found growing in shallow water and in an exposed locality at Long Reaf near Christiansted, St. Croix. Furthermore a speci- men washed ashore at Sandy Point, St. Croix, has been sent to me by Dr. Hambur- ger. ØRSTED does not indi- cate the locality where he found his specimens. Mile. Vickers mentions this species from Barbados in her list and I have specimens of it from Jamaica (Kingston) where it was found by Mr. O. Hansen Ganneskov. Geogr. Distrib. West Indies. Fig. 98. Galaxaura flagellifor?nis Kjellm. Tranverse section of a young thallus with mostly long assimilating filaments in diffe- rent stages of development. (About 150:1). 3. Galaxaura flagelliformis Kjellm. Kjellman, F. R., Om Floridé-slagtet Galaxaura, p. 47. This species was based by Kjellmax upon specimens from Key West, Florida, collected by Bailey and preserved in Herb. Areschoug in Stockholm. 94 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. My specimens seem to agree quite well with those of Kjellman. In a transverse section of the thallus (Fig. 98) it is seen that the medullary layer consists of rather thin filaments woven between each other ; they are of variable breath, their diameter being 12 — 16 fi thick or even more. The supporting cells at the periphery are mostly not much developed; they are irregularly 3 — 4-gonat (Figs. 99 and 100), up to 40 /i in diameter. They carry each a single or more rarely two assimilating filaments, short or long. The short ones (Fig, 99 h, Fig. 100) mostly consist of three cells, someones only of two; the basal cells are large, oval, about 60 — 70// long and 40 IX broad, the others smaller, the uppermost have only a diameter about 27 jx long. The basal cells in the long assimilating filaments (Fig. 99 a) have nearly the same size and shape. The breadth of the cells in the cylin- drical part of the filaments seem to vary somewhat, in one specimen 1 found the dia- meter to be about 16//, in another even 18//; Kjellman states the diameter to be 15 //. The length of the cells is often more than double the breadth. Regarding the habit of the plant the accompanying figure (Fig. 101) gives an idea. The plant is, as pointed out by Kjellman, large, about 16 cm high not much ramified with very long internodes and the branches spreading much and often somewhat recurved at the summits. It is evenly covered with hairs over the whole surface and of a reddish brown colour. This species has been found in deep water only down to a depth of about 20 — 30 meters. Fig. 99. Galaxaura flagellifonnis. a, ba- sal part of long as- similating hair, b, short a'ssimilating filaments, one with two cells, another with three. (About 15() : ij. St. Jan: Off Hermitage and in several pla- ces in the sound between this island and St. Tho- mas. Geogr. Distrib. Florida, West Indies. Fig. 103. Galax- aura flagellifonnis Kjellm. Short assi- milating filament with chromato- phore and pyrenoid in the upper end of the celh (About 175:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 4. Griilaxaura lapidescens (Sol.) Lamx. 95 Lamouroux, J. V. F., Histoire des Polypiers corall. flexibl. 1816, p. 264. Kjellman, F. R., Floridé-Slagtet Galaxaura, p. 39—43. Corallina lapidescens Solander in Ellis and Solander, Natural History Fig. 101. Galaxaura flagelliformis Kjellm. Part of a plant, (About 1,5:1). of many curious and uncommon Zoophytes, London 1786, (ex p., comp, the text below). As pointed out by Kjellman so many different forms occurring in nearly all tropical seas have in the past been referred to Galaxaura lapidescens, originally described by Solander, that it was to be supposed, a priori, that this species comprehended in 96 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. reality several distinct species, all densely haired forms having been referred to it. Referring to the comprehensive survey of Kjellman, quoted above, for further details of this question I only wish to point out here that Solander already mentions two varieties of his Corallina lapidescens. He says (1. c, p. 113) : "There are two va- rieties of this Coralhne, one that is always dichotomous. Tab. 22, fig. 9, and another that sends out three or more joints from the same place, Tab. 21, fig. g," and his description of some speci- mens "preserved in spirits as they were taken out of the sea" in which the "fine short reddish hairs come out in regular whirls or circles", seems to suggest that he has had to do with a third species e. g. G. suhverticillata or a similar one. While Solander nearly always mentions the localities from whence the plants originate, he unfortunately does not give any localities for this species. As is clear from this the founder of the species referred perhaps even three different forms to it and afterwards nearly all long-haired forms have, as pointed out above, been con- sidered as belonging to it. The only investigator who has tried to divide this species is Kützing who in "Tabulæ Phy- colgicse", vol. VIII, p. 38 has two species namely: G. lapidescens and G. tomentosa. But J. Agardh in Epicrisis, p. 530, refers Kützing's species tomentosa to G. lapidescens as a variety only That J. Agardh nevertheless had some doubt how far G. lapides- cens should be separated is evident, as was also pointed out by Kjellman, not only from his remark in Epicrisis, 1. c. : "an plures species hoc loco lateant", but also from what is said in "Till Algernes Systematik", 4de afdeling, VII Florideæ, p. 75. Yet I shall only mention that Askenasy in "Forschungsreise S. M. S. Gazelle", IV Teil, p. 33 with regard to the occurrence of G. lapi- descens says that it is common in all tropical seas. Thus matters stood when Kjellman commenced his thorough investigations. As a result of these studies this species is now divided into a great number of species with more restricted distribution. But as Kjellman had no opportunity to examine the original specimens of Ellis and Solander he did not know with certainty which of his species ought in future to be named lapidescens and among the species which he refers to the group Rhodiira he does not mention it. On the other hand in the introductory remarks to the Rhodiira group he points out that in his opinion this species ought to be maintained and he F. Borgesen: Rhodophyceæ of the Danish W. Indies. 97 adds that he thinks that the plant which Kützing in Tabulæ Phycologicæ, vol. 8, pi. 38, fig. I has figured as G. lapidescens might correctly be considered as this species. However, it seems to me, the figure (pi. 21, fig. g) of Ellis and Solander gives a very good idea of the plant and I think it is more correct to take this the first pubhshed figm-e of the plant, as the type of the species. In spite of this I do not mean that the figure of KtJTZiNG in question would not also represent a form of this species 1). An examination of the original material of Ellis and Solander would of course be the most conclusive but as mentioned in my introductory remarks to this genus the type specimens do not now seem to exist. All the specimens I have found are much ra- mified , forming large d en- se tufts (Fig. 102). These are fastened to the sub- stratum by means of a broad disc from which several branches often arise. These branches are repeatedly subdichoto- mously ramified. The internodes are cylindric of variable length, some- times they are more than 1 cm long sometimes shorter. In the middle of the thallus the diameter of the branches without hairs reach a length of about Fig. 102. Galaxaura lapidescens (Sol.) Lamx. Part of a plant. (About IV2 : 1). 1) As on account of this fact it seemed to be of great importance to examine the two plants upon which Kützing based his draw- ings of Galaxaura lapidescens and Galaxaura tomentosa I asked Mme Weber to allow me to investigate a little bit of the two plants in question which as said by Kützing both originate from Mexico. At my request she greatly obliged me by sending a small piece, enough for microscopical examination, of Galaxaura tomentosa originat- ing from Mexico, but she told me at the same time that in the Herb. Kützing belonging to her there was no specimen of Galaxaura lapi- descens from Mexico. Having examined the piece of Galaxaura tomen- tosa I arrived at the conclusion that this plant of Kützing is like Galaxaura Liehmanni (Aresch.) Kjellm., described as Holonema Lieb- manni 4 years earlier by Areschoug in "Phyceæ novæ", 1854, p. 356. Dansk Botanisk Arkiv, Bd. 3. Nr. 1. (1916.) 7 98 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 1 mm, with the hairs the diameter is more than 2 mm. The hairs are evenly distributed over the whole thallus giving it a felted appearance. The colour is rather variable, in some specimens red- brown in others greyish oHve-green with a more or less reddish tinge. As to the anatomical structure the medullary tissue consists of rather thick-walled filaments woven together. The filaments are of very variable size most often about 11 — 13 /J. broad but some occur which reach more than the double thickness; the diameter of the whole tissue reaches a width of about 650 pt. Towards the periphery these filaments bare the polygonal sup- porting cells commonly found in this group (compare Fig. 103). These are mostly 4-gonal and about 40—50// broad. The assimilating filaments arising from these cells are of two different kinds, some short and others long. In the older parts of the thallus the long assimilating filaments especially occur while the shorter ones usually are very rare, in the young thallus the shorter assimilating filaments are quite as common as the longer ones. The short filaments consist of three, sometimes only of two cells (Fig. 103 6) and these cells decrease ra- pidly in size upwards. The lowest cells are large up to 10 /j. or even longer and about 45// broad, the uppermost ones are only about 28 — 30// broad. The basal cells in the long assimilating filaments are of about the same shape and size as those in the short filaments. Above the lowest largest one, a smaller oval cell follows and sometimes the following cell is yet somewhat swollen in the middle while the rest of the cells in the filament are cylindrical, mostly about Fig. 103. Galaxaura lapidescens (Sol) Lamx. a, long assimilating filaments, b, short assimilating filament and basal part of a long one issued from the same sup- porting cell. (About 150 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 99 I 19// thick reaching a length of up to 2—3 times their own breadth. All walls in the filaments are thick and stratified not only in the basal cells but also in the cyhndrical upper ones (Fig. 104). In the cells of the assimilating filaments a well-developed chromatophore is present (Fig. 104). It lies near the upper end of the cell, is campanulate with long prolongations down the wall of the cell and contains a large pyrenoid in its centre. In the cylindrical cells the pyrenoid lies nearer the middle of the cell. Of the species described by Kjell- MAN this plant seems to come near to Galaxaura Liebmanni. Besides the small type specimen in Herb. Are- scHOUG I have seen some larger ones also collected by Liebmann in Mexico and belonging to the Botanical Mu- seum, Copenhagen. These show that the species has a more robust and thicker thallus, the filaments in the medullary tissue are thicker about 19 ,«, there are often 2 — 3 large cells at the base of the long assimilating filaments and the basal cell of these are some- what larger (about 75 n long and 55 n broad); also the cylindrical part of the long assimilating filaments is thicker, its diameter reaching 22 fjt. Also G. ramiilosa seems to show some likeness to this species, but it differs among other things by the vigo- gorous short assimilating filaments the uppermost cells of which are relatively large, and by the thinner, long assimilating fila- ments. G. lapidescens was found mostly in sheltered places and in shallow water, e. g. in lagoons and bays, once it was taken in the open sea at a depth of about 12 meters. St. Croix: The harbour of Christianssted, off Frederikssted, Lime Tree Bay. St. Thomas: Bovoni Lagoon. Fig 104. Galaxaura la- pidescens (Sol.) Lamx. Basal part of an assimi- lating filament with chro- matophores and pyre- noids; below in the cells the nuclei are made visi- ble by staining. (About 400:1). Geogr. Distrib. : West Indies. 7* 100 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 5. Galaxaura delabida Kjellm. Kjellman, F. R., Om Floridé-slagtet Galaxaura, p. 49. Of this plant I have only seen the original material which is now kept in Herb. Kjellman in the Botanical Museum in Upsala ; it was collected at St. Thomas and distributed by P. T. Cleve. The original material consists of numerous mostly small pieces. Kjellman points out that the most characteristic feature of this species is that the filaments in the medullary tissue differ very much in thickness, and that the supporting cells are often not developed, the assimilating filaments in this case growing directly out from the medullary filaments. The short assimilating filaments often consist of two cells only. The long assimilating filaments are about 15 n broad and have comparatively short cells, V-j^ — 2 times as long as broad. Kjellman supposes that the plant forms low tufts pressed to the sub- stratum. Geogr. Di strib.: At present only known from St, Thomas. Fig. 105. Galaxaura rugosa (Solander) Lamx. Part of a plant. (About IV2 : !)• Sectio II. Microthoé Dcsne, J. Ag, 6. Galaxaura rugosa (Solander) Lamx. Lamouroux, J. v., Histoire des Poly- piers coralligenes flexibles, Caen 1816, p. 263. Kützing, Fr., Tabulæ Phy- cologicæ, vol. VIII, tab. 33, flg. 1. Agardh, J. G., Epicrisis, p. 528. Kjell- MANN, F. R., Floridé-slagtet Galaxaura, p. 55. Corallina rugosa Solander in Ellis, J., and D. Solander, The Natural History of many curious and uncommon Zoophytes, London 1786, p. 115, tab. 22, fig. 3. Kjellman does not give any description or figures of this old species of Solander but refers to the description of J. Agardh in Epicrisis and to the figures of Ellis and Solander, p. 115, tab. 22, fig. 3, and of Kützing in Tabulæ Phycologicæ, vol. VIII, tab. 33, fig. 1. But on the other hand, when describing several new species related to or formerly considered as forms of G. ru- gosa, he points out in what way they differ from this species. The specimens which I refer to G. rugosa (Fig. 105) are cer- tainly very like those I refer to the following species, on the other F. Borgesen : Rhodophyceæ of the Danish W. Indies. 101 Fig. 106. Galaxawa rugosa (Solander) Lamx. Transverse section of the thallus and sur- face cells seen from above. In the cells the campanulate — stellate chro matophores with the pyrenoid in the middle. (About 250:1). hand they show just the differences Kjellman has noted. The most essential and striking difference is the smaller development of the assimilating filaments. The well developed annular groups of hairs found in G. sqiialida in the younger parts of the thallus were not present in these specimens ; only in the older part of the thallus hairs occasionally occurred. The diameter of these hairs was about 16 — 18 /u. The ramification is perhaps somewhat more regularly dichoto- mous in this species, the internodes being nearly of the same length, but variations occur. Owing to the lesser development of the hairs the surface of the plant is almost quite smooth. The annulations are well developed. In the dried specimens the green colour was more promi- nent and the red tinge originating from the hairs in G. sqiialida was lacking. As to the anatomical structure I have not found any differences worth mentioning. The fig. 106 shows a transverse section of the peri- feral tissue ; this consists of 3—4 layers of cells the innermost largest; large lobed cells were common, quite in accordance with that which is found in G. squalida. In a collection from Lime Tree Bay at St. Croix hyaline unicellular hairs were found abun- dantly in the young tips of the plant (Fig. 107). These hairs grow out from the peripheral cells. They are long, nearly cylindric, when full grown about 200— 300 /i long and 6—8;/ thick. The upper end is filled with protoplasm. Their de- velopment seems to agree perfectly with the description of Rosenvinge as to similar hairs in other Florideæ^). Fig. 107. Galaxawa rugosa (Solander) Lamx. Surface cell with long unicel- lular hair. (About 175:1). 1) RosENviNGE, L. KoLDERUP, Remarks on the hyaline unicellular hairs of the Florideæ in BiologiskeArbejder tilegnede Eug. Warming, København, 1911, p. 207. 102 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. This species grows in shallow water and in somewhat shel- tered places. It seems to be common. It has been collected in the following places. St. Croix: Coakley Bay, Christianssteds Har- bour, Rust up Twist, Cane Garden, Sandy Point, Lime Tree Bay. Some old specimens from St. Thomas, collected by Ravn, are found in the collections of the Botanical Mu- VU seum, Copenhagen. Geogr. Distrib. : West Indies. 'OÉå i% Fig. 108. Galaxaura squalida Kjellm. Part of the thai! us showing the groups of hairs occurring now and then espe- cially in the young parts of the thal- lus. (About 1,5:1). Fig. 109. Galaxaura squalida Kjellm. Transverse section of the thallus with lobed cells and assimilating filaments, one of which is ramified. (About 150 : 1). 7. Galaxaura squalida Kjellm. Kjellman, F. R., Om Floridé-slagtet Galaxaura, p. 55. This species has been described from specimens collected at St. Croix by Ørsted and preserved in Herb. Areschoug in Stock- holm. In the herbarium of the Botanical Museum, Copenhagen, I have found several of Ørsted's specimens belonging to this species. The description below is especially based upon my own material. The plant (Fig. 108) forms dense richly ramified tufts which are fixed to the substratum by means of a broad disc composed F, Borgesen: Rhodophyceæ of the Danish W. Indies. 103 Fig. 110. Galaxaura squalida Kjellm. Transverse section of the thaUus show- ing the periferic tissue with chroma- tophores and pyrenoids. (About 250:1), of numerous irregularly bent filaments felted together ; these fila- ments have fairly thick walls and a breadth of about 16 /i while their length is often up to ten times the breadth. From this base several branches grow up and these are re- peatedly dichotomously ramified. The internodes are of very variable length from one to two cms. The branches are cylindrical, also in the dried condition, with the exception of the quite young upper ends, not yet much incrusted which collapse being more or less flat when dry. In the spirit material the apices are nearly cup-shaped with the sunken growing point in the middle. The colour of the dried plant is a sordid yellow-green with a red-brown tinge espe- cially where the assimilating hairs are present. These do not occur evenly distributed over the whole surface; they are most numerously present upon the younger parts of the branches and often show here an annular arrangement but quite scattered ones also often occur especially upon older parts of the thallus. The surface of the plant is mostly rather clearly annulated. A transverse section shows that the medullary tissue is composed of rather thick- walled dichotomously branched filaments con- sisting of long cylindrical cells of which the diameter varies from 7 to 16 /i. The periferal tissue consists of short often dichotomously ramified cell-threads composed of 3—4 cells (Figs. 109, 110). Of these the innermost are the largest; they are mostly roundish but very large ones, irregularly shaped and lobed are often found (Figs. 109, 111). These lobed cells are also men- tioned and figured by Kjellman and occur in several other species. This cell layer is about 40 /i thick, but the cells are very variable in size the large lobed cells being often much thicker. These cells are colourless and contain only protoplasm, cell sap etc. The next cells are smaller (about 25— 30/i in diameter), nearly Fig. 111. Galaxaura squalida Kjellm, A lobed cell from the periferic tissue. (About 200:1). 104 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 112. Galaxaura fragilis Lamk Part of the thallus. (About li/^ : 1) spherical and have rather well developed chromatophores. Finally we arrive at the epidermal cells, the real assimilating ones. These are short, 10— 12/^ long and 20—24/^ broad, in transverse sec- tion often triangular, when seen from above 5— 7-gonal and closely united (comp, those found in G. squalida, Fig. 106). They contain a well developed cam- panulate chromatophore with long branched prolongations running down along the walls of the cells (Fig. 110); in the middle of the chromatophore a pyrenoid is present. But be- sides this, the real assimilating tissue, the plant possesses the above mentioned assimilating fdaments (Fig. 109); these are composed of a row of cells which are abuot 2—3 times as long as broad (lat. about 15—18 fj) and have thick walls, 4 ^ thick. They contain a much ramified chro- matophore. The chalk incrustation is richly developed and found through- out the whole tissue. A specimen from the harbour of Christianssted had ap- parently ripe cystocarps. These are nearly spherical with an opening above. The carpospores are large, oval, about 50 fi long and 30 ^ broad. My specimens seem to agree very well with the description of Kjellman and with the original specimens from St. Croix. As pointed out above with regard to G. rugosa, this species is nearly related to the present one; for the differences between them I refer to the comparative remarks given above. Galaxaura squalida has been ga- thered both in shallow water in more sheltered places and in deeper water at a depth of about 30 meters and in more open sea. It was found in the following localities: St. Croix: Christianssteds Harbour, off Frederikssted. At the shores of this island it was also col- Fig. 113. Galaxaura fragilis Lamk. a, epidermal cells seen from above, b, fila- ments from the dia- phragms. (About 250 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 105 lected by Ørsted. St. Jan.: Coral Bay, and in the sound between St. Thomas and St. Jan near the island St. James. Geogr. Distrib.: West Indies. Sectio III. Euffalaxauva (Dcsne) Kjellm. 8. Cralaxaura fragilis (Lamk.) Kütz. KüTziNG, Spec, p. 530. Kjellman, F. R., Floridé-slagtet Galaxaura, p. 60. Dichotomaria fragilis Lamk. Lamarck, J., Histoire naturelle des ani- maux sans vertebres, t. II, 1816, p. 145. The specimens (Fig. 112) have a glabrous, when dry often shining surface. The annulation which in some of the specimens determined by Kjellman was very prominent was not so distinct in my plant. The branches are fairly regularly dichtomously forked. The internodes are 4 — 5 mm long, mostly slender at their base growing thicker upwards, more rarely nearly cylindrical ; at their base an annular bursting of the calcareous layer is often present. The colour of the dried plant is light yellow green often also more reddish. The whole plant is very fragile. A transverse section reveals the fact pj^. ^^^ Galaxaura fragilis that the medullary tissue is very (Lamk). Transverse section of loose; it consists of dichotomously t^e thallus. (About 250:1). ramified, rather thick -walled fila- ments running between each other ; their diameter is about 8 /j. long. The diaphragms at the joints the presence of which espe- cially characterizes the Sectio Eugalaxaura are formed in the following manner. Numerous filaments are crowded more firmly together and furthermore the ends of these filaments are much thickened, their diameter reaching often lip. or more (Fig. 113 6). The peripheral tissue (Fig. 114) is about 70// thick. It consists of short, dichotomously branched filaments the cells of which form together a parenchymatous tissue; with the except- ion of the epidermal cells, all other cells in this tissue are easily separable after decalcification. The innermost cells are the largest; they are roundish in shape and their diameter reaches a length of about 35//. Towards the periphery the cells grow smaller, the epidermal cells being the smallest ones. These are fairly strongly united and when seen from above 5 — 6-gonal 106 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. (Fig. 113 a), about 14 ^ broad, while their length in transverse section is seen to be about 8// only. The chromatophore is found in the upper end of the cells; it has the common campanulate shape with a pyrenoid in the middle. It is most developed in the epidermal cells, but it is in the whole not especially large. Kjellman points out that judging from Ellis and Solan- der's figure 4, plate 22, it is not impossible that the plant which here is called CoraUina ajlindrica is not the species we now call cy- lindrica but the present one. In considering this figure, it certainly can not be denied, that the length of the internodes are in pro- portion to their breadth too short, and that in this respect the figure agrees better with G. fmgilis. But to state this with cer- tainty an examination of the original specimen is necessary. This species has been found in a depth of about 12 meters in more open sea. Only found once at St. Croix: off Frederikssted. Geogr. Distrib. : West Indies, Atlantic coast of South America. 9. Galaxaura cylindriea (Solander) Kjellm. Kjellman, F. R., Om Floridé-slagtet Galaxaura, p. 64. CoraUina cylindriea in Ellis, J., and D. Solander, The Natural History of many curious and uncommon Zoophytes, 1786, p. 114. I have not collected this plant myself but in the Botanical Museum, Copenhagen, several large specimens collected at St. Croix by Øested are to be found. Ørsted does not give any more definite information as to where he gathered the plant. Some of the specimens reach a length of more than 12 cm; such a large specimen of Ørsted determined by Kjellman is also found in Herb. Areschoug in Stockholm. Regarding an eventual change of name I refer to what is said about Galaxaura jragilis. Geogr. Distrib.: West Indies, Atlantic coast of South America. Sectio IV. Brachyclculia Sonder, Kjellman, 1. c. p. 67. 10. Galaxaura marginata (Solander) Lamx. Lamouroux, J. v.. Hist. Polypiers corall. flexibl., 1816, p. 264. Kjell- man, Floridé-slagtet Galaxaura, p. 77. CoraUina marginata Solander in Ellis and Solander, Nat. Hist. Zoo- phytes, p. 115, tab. 22, fig. 6. F. Borgesen: Rodophyceæ of the Danish W. Indies. 107 Zanardinia marginata J. Ag., Spec. Alg., vol. Ill, p. 534. Brachycladia marginata Schmitz, System. Übersicht d. bisher bekannt. Gatt, der Florideen (Flora, 47, 1889, p. 438). This species was founded upon a specimen collected at the Bahama Islands. The de- scription of Kjellman on the other hand is based upon a specimen in Areschoug's Her- barium in Stockholm and on which he remarks that it was collected at the coast of South America at Bahia (?). But among the material of Ga- laxaiira in Herb. Areschoug which I have seen, no such a specimen is present ; on the other Fig. 115. Galaxaura marginata (Solan- der). Part of a plant (About 1,5 : 1). hand one is found collected by LiEBMAN at Havana and determined by Kjellman as G. marginata. Most prob- ably this is the specimen he refers to. Kjellman points out that the specimens examined by him agree well with the figure of SoLANDER, and as both plants also have been collected in nearly the same area he considers himself en- titled to refer Areschoug's specimens to Solander's species. The rather numerous specimens (Fig 115) I have collected seem in all essen- tials to agree with the de- scription of Kjellman. They differ from it in one respect, however, the assimilating peri- pheral cells ending commonly, but not always, in a short api- culus (Fig. 116), in a similar way to that described by Kjellman for his species, Galaxaura apiculata from Japan. This short api- Fig. 116. Galaxaura marginata (Sol.). Transverse section of the perif eric tissue of a form with apiculated assimilating cells. (About 250 : 1). 108 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. cuius is not always present and in one specimen of mine (Nr. 1317) the mucronated assimilating cells were rare, nearly all had a broadly rounded summit (Fig. 117). The specimens I have collected formed rather large and dense tufts composed of numerous richly ramified branches. At the base the main branches are terete or nearly so but higher up all the branches become quite flattened. They are either repeatedly forked or irregularly ramified (Fig. 115). The colour of the dried plant is greyish to olive-green with a reddish tinge especially in the upper parts. The surface is dull and when seen under a lens finely dotted, this appearance ori- ginating from the closely placed but free assimilating cells. In this respect it differs from the Galaxaura occidentalis, mentioned below, this having a more even and often shiny surface while both plants otherwise show a striking remblance in their habit and where grow- ing together. In the dried specimens the edges of the branches are often somewhat pro- minent giving the branches a chanelled appearance. In my specimens the transverse stri- ations were not much developed some- times not at all; when present they were mostly found towards the summit of the branches (Fig. 115). With regard to the flattening of the branches some differences are present in the various speci- mens. In some (my collection nr. 1317 a) a transverse section of the thallus is nearly oval, while in others (nr. 1657 b) this was oblong linear with quite parallel sides. In specimens pre- served in spirit the branches are also clearly flattened (compare the branch to the right in Fig. 115) but not as much as is the case with the dried specimens ; their edges are rounded and they show no trace of being channelled. A transverse section of the thallus shows that the medullary tissue consists of irregularly, subdichotomously ramified filaments running between each other in the mucilage found here; they have rather thick walls and a diameter of about 14;/, but both thicker and thinner are present. Outwards these filaments bear Fig. 117. Galaxaura mar- ginata (Sol.). Transverse section of the periferic tissue. (About 200 : 1). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 109 the parenchymatous tissue (comp. Figs. 116 and 117) ; this consists of 2—4 layers of cells of which the innermost are the largest; the cells are nearly colourless and rather loosely connected. From the periferal smaller cells in this tissue the short assimi- lating filaments arise. These are composed of the smaller sup- porting, more or less clavate cells with proportionally broad summit and the large assimilating cells. The shape of the last mentioned is rather variable, sometimes longer, oblong-oval to sub- cylindric (long. = 57 ti, lat. = 27 /x) sometimes shorter, broad oval (long. = 45 //, lat. = 30 ß) and they are mostly, as mentioned above, provided with a short apiculus. The chromatophore (Fig. 116) is well developed; it is parietal, placed in the upper end of the cells, bell-shaped, with long thin prolongations downwards along the walls of the cells. In the middle at the top of the cell it contains a pyrenoid. Also the supporting cells contain a chro- matophore but lesser developed. In the space between the supporting cells the chalk incru- station is present as an annular ring giving firmness and cohesion to the thallus. The assimilating cells protude freely over the chalk incrustation. The material examined was sterile. ]\/[iie Vickers in her "Liste des Algues de la Barbade" re- ports Galaxaiira apiciilata from Barbados. I have not seen her specimens but feel convinced that she has had similar apiculated specimens before her and which I prefer to refer as explained above to Galaxaiira marginata and not to the Japanese plant, G. apiculata. This plant has been found in shallow water in a sheltered locality. St. Croix: The Harbour of Christianssted. Geogr. Distrib. : West Indies, Atlantic coast of South America. Sectio V. Vepreculæ Kjellm. 11. Galaxaura occidentalis nov. spec. G. frutescens, densa, stipitata, stipite subtereti, fronde dichotomo-ramosa, inferne subtereti, superne complanata, sic- cata canaliculata, sordide griseo-olivacea, membranacea, super- ficie inferne splendore carente, in superiori parte sæpe irides- cente. Internodia in basi contracta, 2 — 3 mm lata. Papillæ in 110 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 118. Gala.vaura occidentalis nov. spec. Parts of the thailus. The figure to the left from a specimen preserved in alcohol, that to the right from a dried specimen. (About 1,5 : 1). fronde juveniliori numerosissimæ, rectæ, clavatæ — subcylin- dricæ, summo mucronatæ, ca. 40 /i longæ et 11 pt latæ. The base of the plant is a broad disc by means of which it is fastened to the substratum ; it consists of numerous rhizoidal fila- ments. These are dichoto- mously ramified and com- posed of cylindrical, nearly colourless cells, with uneven walls, about 14 u thick. From this basal part the erect shoots (Fig. 118) grow up in all directions. These are much branched and the ramification is more or less regularly dichoto- mous. In the lower part the thallus is terete but it soon grows flat; in the dried plant the edges are mostly prominent the thallus thus getting a ca- naliculate appearance (compare Fig. 118). The branches are about 2 — 3 mm broad and about 1 mm thick ; the internodes taper somewhat below and are often jointed at the base. The plant preserved in spirit is not canaliculated but has broadly rounded edges. The colour of the dried plant has a greyish or dirty olive- brown tinge; in the lower part the sur- face is dull and of a mealy appearance ; in the upper young parts often smooth and glossy, sometimes shining like mother of pearl and of a light greyish - yellow colour. Fig. 119. Galaxaura occidentalis nov. spec, a, transverse section of the periferic tissue showing lobed cells, b, the lowermost cells in in the peripheric tissue seen from above. (About 200 : 1). F. Børgesen : Rhodophycea of the Danish W. Indies. Ill Cutting a transverse section we find that the thallus con- sists in the middle of irregularly most often dichotomously ra- mified cylindrical filaments which run in all directions in the mucilage found here; they have a diameter of about 8// but both thicker and thin- ner also occur. The peripheral tissue (Figs. 119 and 120) reaches a thick- ness of about 90,«, not count- ing the papillæ. The inner- most cell-layer has the largest cells ; these are rounded poly- gonal, rather closely united, about 70// broad and 40« high but larger and smaller ones also occur. The cells in the middle are smaller, roundish, but larger lobed cells are common (Fig. 119 a); the cells in this layer are about 30 iJL high. Between Fig. 120. Galaxaura occidentalis noy. spec. Transverse section of the peri- pheral tissue shovving the campanulate chromatophores with the large pyre- noid above. Below the nucleus is maid visible by staining, (About 370:1). these cells and the epidermal ones many and often large intervals are present, here the chalk incrustation especially is found forming a circular belt round the whole thallus. The epidermal cells are closely united ; they are rounded-trigonal when seen in transverse section (Figs. 119, 120), 5— 7-gonal when seen from above (Fig. 121). They are about 16 /i high and their diameter varies from 18— 30/i. They have a well developed, campanulate chromatophore with a central pyrenoid (Figs. 120, 121). Also in the cell-layer below the cells have chromatophores but less developed while the innermost cells have no chromatophores at all. Finally growing out from nearly all the surface cells we find the onecelled papillæ, characteristic to the group of Vepreculæ, by means of which the capacity of the assimilating tissue is so highly increased. The Fig. 121. Galaxaura occidentalis nov.spec. Epidermal cells seen from above showing the elegantly shaped chromatophore with the pyrenoid in the middle. (About 500:1). 112 Dansk Botanisk Arkiv Bd. 3. Nr. 1. Fig. 122. Galax- aura occidenta- lis nov. spec. Papillæ growing- out into hya- line hairs. (About 370 : 1). internodes and papillæ (Figs. 119 a, 120) protrude freely over the surface of the thallus and are not included in the chalk incrustation. In shape they are clavate-cyhndrical, having their largest diameter a little above their middle and then abruptly narrowed in, running out into a short apiculus. They are about 40 /u long and 11 ,« broad in their broadest part. They are provided with a well developed chromatophore (Fig. 120), parietal, cuphke, with thin prolongations along the wall of the cell ; in the middle a pyre- noid is present. Occasionally I have found 1 — 2 small cells at the summit of the papillæ which is then rounded and very rarely the up- per cell was also growing out to a long one- celled hair richly filled with protoplasm at the upper end (Fig. 122). Antheridial conceptacles (Fig. 123) were pre- sent in great numbers. They occur in the young are nearly spherical bodies wilh an opening through the wall of the thallus. Their wall consists of ramified filaments with larger cells growing closely together. From the innerside of these the richly ramified antheridia pro- ducing filaments grow up in the cavity. The anthe- ridial filaments are divided into small cells of which those at the apex (but later on also the other cells) are transformed into mother-cells for the sper- matia. The antheridia are about 8 fj. long and 5 fj. broad, oval. The anthe- ridial conceptacles have mostly a diameter of about 200—300 fjt but larger ones also occur. To the Sectio Vepre- ciilæ Kjellman only refers four species none of which are from the West Indies. Of these G. vepreciila Kjellm. seems to come very near to my plant. I have been able te compare my plant Fig. 123. Galaxaura occidentalis nov. spec. Transverse section of anantheridial con- ceptacles. (About 200 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 113 with the original specimen from Madagascar and sent to Kjell- MAN from E. BoRNET under the name of G. marginata. Both plants grow in dense tufts. But my plant is not so much incrusted with chalk, the thallus is thinner, the internodes are less broad at their base. Further G. vepreciila differs from my species by having an entirely dull surface and by being more light yellow-green with a reddish tinge. To judge from Kjellman's description and figures the anatomical structure seems to come very near in both plants; but the pa- pillæ in my plant are longer and relatively more slender than those in Kjellman's plant which besides have also often a round- ish apex. And G. infirma Kjellman from Sandwhich Island which has also the internodes somewhat narrowed differs from my plant in its thicker, dull, not shining and rather rugose thallus and by the different form of the papillæ. However, the original speci- mens are some small fragments and a comparison is therefore difficult. The two other species, Galaxaura hystrix Kjellm. and Galax- aura ventricosa Kjellm. seem to show more differences. In a paper: "Notes on the species of Liagora and Galaxaura of the Central Pacific"^) F. K. Butters has described a Galaxaura spec, which seems to come very near to my plant; but to judge from the very short description some minor differences are present : the Pacific plant seems to be more distinctly contracted and jointed at the base of the internodes and the size and shape of the papillæ also show some differences. Galaxaura occidentalis I have found only once in shallow water and in sheltered place; in the collections of algæ in the Botanical Museum, Copenhagen, two old specimens are found, one from St, Croix and another with the indication "Antillis 1836". St. Croix: The harbour of Christiansted. 1) In "Minnesota Botanical Studies", Vol. IV, part II, Minneapolis 1911, p. 183. Dansk Botanisk Arkiv, Bd. 3. Nr. 1. (1916.1 8 114 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fa/77. 3. Gelidiaceæ. Gelidium Lamour. 1. Gelidium corncum (Huds.) Lamour. Lamouroux, J., Essai . . . Thalassiophytes (Annales du Museum, vol. XX, 1813, p. 128). Bornet, E., Les Algues de P. K. A. Schousboe, 1892, p. 270. Fucus corneus Huds., Fl. Anglica, 1778, p. 585; Turner, Fuci, vol. IV, 1819, p. 146. var. pinnata (Huds.) Turner. Turner, 1. c, p. 146, tab. 257, fig. d. Fucus p inn atiis Huds., Fl. Anglica, tome II, 1778. p. 586. Gelidium cærulescens Crouan in Maze et Schramm, Algues de Guade- loupe, 1870—79, p. 109. Collins, F., The Algæ of Jamaica, p. 252. Non Gelidium cærulescens Kiitz., Tab. Phycol. vol. 18, p. 19, tab. 56. The plant (Fig. 124) I here refer to this species seems to agree fairly well with the above quoted figure of Turner. It is the same which the brothers Crouan, 1. c. p. 199, have referred to Gelidiiun cærulescens Kütz. By means of an original specimen of Maze et Schramm's Algues de la Guadeloupe I have been able to state its identity. Collins has found the same plant (distributed in Phycotheca Bor. Am,, Nr. 783) in the collections of algæ from Jamaica which he has worked out and in his publi- cation: "The Algæ of Jamaica" (Proceedings of the Amer. Acad, of Arts and Sciences, vol. 37, 1901) he calls it (p. 252) Gelidium cærulescens Crouan. Concerning the use of this name he adds : "By the kindness of Dr. Bornet this plant has been compared with authentic specimens from Guadeloupe, and it is the plant referred to by Maze & Schramm, Algues de Guadeloupe, p. 199. Whether it is the plant of Kutzing, Tab. Phyc, vol. XVIII, pi. 56, from New Caledonia, is not certain." As it seemed to me of great interest to know how far Kützing's plant and that of Crouan agreed I sent one of my specimens to M°^° Weber and asked her to do me the favour of comparing my plant with the type specimen in Herb. Kutzing. M*"** Weber obliged me by making such comparison and she tells that there is only a single specimen in Herb. Kutzing namely the one figured in "Tabulæ"; the specimen is much like the figure, the shade of the colour may be a little darker in this plant but that is the only difference. Further M"^^® Weber writes: "The specimen bears tetraspores at the top of almost every branch. Can this F. Børgesen: Rhodophyceæ of the Danish W. Indies. 115 be the reason why all the tops are blunt? I don't know and I should want more specimens to judge the species well. As mat- ters stands my type specimen differs from the specimen you sent me," And M'"'" Weber adds that she thinks that the West Indian plant is very much hke Gdidium corneum to which spe- cies I also think it may rightly be referred. As mentioned above my specimens (Fig. 124) agree well with Turner's figure of his var. g. pinnata yet they are somewhat smaller and often only bipinnate. The West Indian specimens too are very similar to a specimen of Gelidium corneum from Ceylon distributed by Harvey ("Ceylon Algæ", No. 31). The specimens found are about 5 cm high. The thallus is flat, reaching a breadth of about 2 mm, seldom more. The apices are blunt with a somewhat sunken growing point. The thailus is mostly bipin- nate, seldom tripinnate and the ramification upon the whole is rather irregular and parts of the thallus are often destitute of branches. A transverse section agrees with the description of Haufe^). The tissue consists of a medullary layer and a cor- tical layer. The former consists of rather long cylindric colour- less cells. The cortical layer, on the other hand, is composed of a few layers of red-coloured, short cells, radially arranged round the periphery of the thallus. Between the cells of the medullary layer the hyphæ-like filaments characteristic of Gelidium are found in abundance. The material was sterile. This species has been found only in the more sheltered places. Fig. 124. Gelidium corneum (Huds.) La- mour. Habit of the plant. (About 2 : 1). 1) Haufe, Fr. E., Beitrage zur Kenntnis der Anatomie und theilweise der Morphologie einiger Florideen. Inaugural-Dissertation. Görlitz 1879. 8* 116 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 125. Wrängelia Argus Mont. Disc- shaped haptera growing out from a basal cell in a ramulus found in the lowermost prostate part of the thallus. The upper large cell in the main filament is broken off. I About 150:1). Wrangelia plebeja J. Ag., Spec. Alg., vol. II, pars. 3, 1863, p. 707: Epi- crisis, 1876, p. 623. This species especially differs from Wrangelia penieillata in its small size being seldom more than 1 — 11/2 cm high, the acute ends of the filaments composing the ramuli and the lack of a dense cortical layer. The West Indian specimens are as to their external habit much hke figure 4/ of Mon- TAGNE, 1. C. Wrangelia Argus is a littoral alga growing even in rather ex- posed places. It is fixed to the substratum by means of nume- rous, often very robust hapteræ which grow out from the basal cells in the ramuli found in the lowermost more or less prostrate St. Croix: in several lo- calities near Christiansted in the harbour. Long Reef, Lt. Princess. Geogr. Distrib.: Warmer parts of the Atlantic Ocean, Mediterranean Sea, Ceylon etc. Fa/77. 4. Wrangeliaceæ. Wrangelia C. Ag. 1. Wrangelia Argus Mont. Montagne, J. F. C, Sylloge generum specierumque Crypto- gamarum, Paris 1856, p. 444. Griffithsia Argus Mont, in Webb et Berthelot, Hist. nat. des iles Canaries, vol. III, Sectio III, Paris 1836—50, p. 176, tab. 8, fig. 4. Fig. 126. Wrangelia Argus Mont. Upper end of a branch with ra- muli and tetrasporangia. (About 80 : 1). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 117 parts of the principal filaments (Fig. 125). As mentioned above, the large cells in the principal filaments lack a dense cortical layer, yet an attempt at this is present, as from the basal cells in the ramuli some very ramified filaments grow out and bend themselves round the large cells in the principal filaments (Fig. 125). The cells in the principal filaments are about 225 [i broad and about four times as long. The ramuli are more rcjbust than those in Wrangelia peni- cillata which is the natural outcome of the littoral occurrence of this alga ; the single cells of the ramuli are proportionally short and broad, the fila- ments become evenly narrower towards the apex and end with a short, acute, conical cell (Fig. 126). In this species tetraspores only were found (Fig. 126). Like the tetrasporangia in Wrangelia penicillata they are terminally placed upon the ra- muli and are sur- rounded by short fi- laments more closely pressed to the tetra- sporangia than in Wrangelia penicillata. They are tetrahedrally divided and their diameter reaches about 60 p. In referring the Wrangelia plebeja of J. Agardh to Montagne's species I make this statement upon specimens determined by Agardh and collected at St. Croix by Ørsted. Certainly the description of Montagne is not especially exhaustive but his figures are of much help. This species has been found at St. Thomas: In several places in the harbour and in Store Nordsidebugt. At St. Croix it is as mentioned above collected by Ørsted. Geogr. Distrib. : West Indies. Canary Isles. Fig. 127. Wrangelia bicuspidata nov. spec. Habit of a plant. (About natural size). 118 Dansk Botanisk Arkiv, Bd. 3. Nr. 1 2. Wrangelia bicuspidata nov. spec. Frons mediocris, ca. 7 cm alta, cæspitosa, ramosa, ecorticata vel in ramis principalibus subcorticata, in superiori et inferiori parte cellularum magnarum filis decurrentibus et assurgentibus, ex cellulis basalibus ramellorum ortis, munita. Cellulæ in ramis principalibus permagnæ, subcylindricæ, 120 n latæ et 10-plo longiores, in superiori parte ad genicula verticilla- tim ramellosæ, ramellis mol- lissimis, pluries dichotome divisis, a basi ad apicem leniter tenuioribus, termi- nali articulo generaliter bi- cuspidato, cellulis in parte basali ca. 50/^ latis, supre- mis ca. 1 /i latis. Fructificatio ignota. All the specimens found were sterile so in referring them to Wrangelia I have only had the vegetative thallus to rely on, but this shows so much likeness to the other species of Wran- selia that I have no hesi- tation in referring it to this genus. As being especially characteristic of this plant may be mentioned the fact that the cor- tical layer is not much developed and that the apices of the assimilating filaments mostly end in two short acute conical cells. Wrangelia bicuspidata is a sublitoral alga growing in rather deep water, 20—30 meters or more. It is an epiphyte, as in the case of Wrangelia penicillata found upon different large algæ, e. g. Caulerpa, Halimeda, Avrainvillea etc. and is fixed to these by means of thin rhizoids growing out from the lowermost parts of the filaments. The plant has a beautiful rosy colour and forms loose, flabby tufts up to seven cm or more in height (Fig. 127). The principal Fig. 128. Wrangelia bicuspidata nov. spec. Part of a main branch with the basal parts of the branchlets from which fila- ments grow out upwards and downwards. (About 60 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 119 filaments consist of very long, nearly cy- lindrical cells (comp. Fig. 128) about 120^« broad and about ten times as long; these cells are thickest near the base, taper slowly upwards growing somewhat thicker again at their uppermost ends and have rather thick walls. At the upper end these long cells carry a whorl of branchlets. These are repeatedly subdichotomously ramified growing evenly thinner towards their apices which end in a single or, usually two, seldom three short conical cells (Fig. 129). From the basal cells of the branchlets several ramified filaments grow out, some upwards some downwards, bending themselves round the large cells of the principal branches (Fig. 128). In the upper parts of the branches where the cells are shorter they often cover the whole cell (Fig. 130) while in the older parts it is only the upper and lower parts which they surround. As a rule those filaments lie quite loose round the cell (compare Fig. 128). The branchlets are as is commonly the the case in Wrangelia crowded together in the upper, young ends of the branches, lower down the whorls of branchlets are more distant in accordance with the lengthening of the large central cells. In the lowermost part of the branches the branchlets fall off. Compared with Wrangelia Argus our plant reminds of this species as to its loose cortical layer but differs from it in its much larger and more loosely constructed thallus and further by the bicuspidate ends of the branchlets. And W rangelia penicillata especially differs from this species by its continuous cortical layer in the principal filaments, by the blunt ends of the branchlets, by its much larger size etc. Fig. 130. Wrangelia Wrangelia biciispidata has been found in bicuspidata now.spec. the sublitoral region down to a depth of Part of a young i ^,/^ ^^ branch. (About 80:1). about oO— 40 meters. Fig. 129. Wrangelia bicuspidata nov. spec. Apices of branchlet. (About 60 : 1). 120 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Found in several places at St. Jan in the sound between this island and St. Thomas where it seems to be common. 3. Wrangelia pcnicillata C. Ag. Agardh, C, Spec. Alg. II, p. 138. Agardh, J., Spec. Alg. II, pars III, p. 708; Epicrisis, p. 623. Derbes et Solier, Memoire, p. 71, pi. 18, figs. 6 — 8. KüTziNG, Spec, p. 664. Harvey, Nereis Bor. -Am., Part 11, p. 143, tab. 34 B. BoRNET et Thuret, Notes algologiques, Fasc. II, 1880, p. 183. pi. 48. Zer- lang, O. E., Entwicklungsgesch, Untersuch, über die Florideen-Gatt. Wran- gelia und Naccaria (Flora, 47, 1889, p. 371). G/iffithsia penicillata Agardh, Systema Alg., p. 143. Dasya spinella Duby, Second memoire sur le groupe des Céramiées, p. 13, tab. II, figs. 3, 4, 5 and tab. Ill, ligs. 1, 2. In the West Indian seas this plant attains a great size especially when it is growing in deep water. Several of the specimens reach a height of 20 cm or even more. The specimens growing in shal- low water are smaller and more robust and more like the Euro- pean specimens while the speci- mens from deep water are more flabby, thinner and in all re- spects more elongated. As to the American form see Harvey, 1. c, where a description and good figures of this plant are found. Zerlang has 1. c. given a very detailed description of the development and structure of this plant to which the reader is referred. I shall only mention briefly that the main filaments in an early stage of development become bare at their base while higher up they carry the verticillate branchlets at each joint. From each of these whorls a smaller branch issues and these branches are regularly alternating. Some of these branches grow out mto long branches and serve to form the ramification of the thallus, most of them in the sterile plant soon die away and fall off; in the fertile plant, on the other hand, they carry the organs of fertilization and last longer. The branchlets are subdichoto- mously branched, thin and soft. At the apices of the branches the branchlets are bent upwards and more or less cover the growing point of the branch, giving all the short branches a penicillate appearance. The ends of the filaments in the ramuli are blunt. Fig. 131. Wrangelia penicillata C. Ag. Part of a plant with tetrasporangia. (About 200 : 1). F. Børgesen : Rhodophyceæ of the Danish W. Indies. 121 All the larger filaments are covered with a cortical layer (comp. Fig. 132) formed by the rhizoids growing out from the base of the branchlets; in the young parts of the branches this cortical layer is not yet developed. The tetrasporangia (Fig. 131) of wdiich Derbes et Solier, 1. c, pi. 18, flg. 7, give a figure are placed terminally upon the short ramuli. The cells from w^hich the tetrasporangia originate give rise also to some short filaments which are more or less curved round the tetra- sporangia forming in this way a kind of involucre. The tetrasporangia are spherical, tetrahedrally divided; their diameter reaches a length of about 75^. The branch which carries the tetrasporan- gia-bearing branchlets are, as pointed out by Zerlang, mostly with- out a cortical layer. The antheridial stands (Fig. 132) are spherical bodies termin- ally placed upon the ramuli and, in a similar way as the tetraspor- angia, surrounded by curved cells growing out from the cell which carry the antheridial stand. This consists of numerous short filaments radiating out from the middle of the stand and at the end of which the spermatia are formed. The diameter of the antheridial stand reaches a length of about 60,«. Duby has 1. c, pi. II, fig. 4 given a figure of a branch with antheridial stands. In the branches which carry the ramuli wdth antheridial stands I have mostly found the cortical layer very well developed. The cystocarps are spherical and terminally placed upon short branches. Regarding their shape and development upon the whole Bornet et Thuret, Schmitz and especially Zerlang have given detailed descriptions and the first mentioned have further given very fine illustrations, I. c, pi. 48. To these descriptions Fig. 132. Wrangelia penicillata C. Ag. Part of a male plant with antheridial stand. (About 200 : 1). 122 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. and figures I must refer for details. The few trichogynes I have seen seem to be somewhat longer than those drawn by Bornet and Zerlang. The tetraspores, antheridia and cystocarps occur in separate individuals ; these organs were found in the months of February and March. This species seems to be common in the sublittoral region down to a depth of about 30 meters and is found as an epi- phyte upon larger algæ, e. g. Caiilerpa, Penicillus, Udotea etc. St. Croix: Near Buck Island. St. Jan: in many places in the sound between this island and St, Thomas. Geogr. Distrib.: Mediterranean Sea; the warmer parts of the Euro- pean and American coasts of the Atlantic. II. Cryptonemiales. Fam. 1. Grateloupiaceæ. Halymenia C. Ag. 1. Halymenia Floresia (Clem.) Ag. Agardh, C, Spec. Ag. I„ p. 209; Systema, p. 243. Agardh, J., Alg. Mediterr. & Adriat., p. 96; Spec. Alg., II., p. 205; Epicrisis, p. 138. Kützing, Spec. Alg., p. 716; Tab. Phycol, vol. 16, pi. 88—89. Harvey, Nereis Bor.- Am., vol. II, p. 193. Berthold, Die Cryptonemiaceen des Golfes von Neapel (Fauna und Flora des Golfes von Neapel, XII. Monographie, 1884). Fucus Floresius demente, Ensajo sobre las variedades, 1807, p. 312. Turner, Fuci, pl. 256. Of this species I have collected a few specimens some of which are rather large reaching a length up to 40 cm. They are all very much ramified and compared with the specimens distributed in Phycotheca Bor. -Am., Nr. 298 thinner and flab- bier and of a paler rosy colour. This is most probably due to their development in rather deep water. On the other hand my plants are much like a specimen from Jupiter Inlet, Florida, collected and most kindly sent to me from Mrs. G. A. Hall. Halymenia Floresia is fixed to the substratum by means of a small disc. Immediately above this the thallus is terete, but it very soon becomes flattened and passes evenly over into the I F. Borgesen: Rhodophyceæ of the Danish W. Indies. 123 leaf-like thin part of the thallus. This is much ramified. The branches or proliferations issue along the margin of the frond and these are again branched in the same way several times; the ultimate ramifications in my specimens are long and narrow and taper evenly against the summit. A transverse section shows that the medullary layer is of a very loose consistency with very much mucilage between the hyphæ-like filaments of which it consists and between which thicker ones grow out in all directions. The cortical layer con- sists of more roundish cells; these are small, oblong-cylindrical and closely placed at the periphery, large and more loosely ar- ranged innermost. Where the cortical layer passes over into the medullary tissue, scattered starlike cells are found with long thin prolongations, radiating in all directions and fusing together with those from the neighbour cells. The specimens found have tetrasporangia. These occur scat- tered over the whole surface and are formed in the cortical layer. They are cruciately divided but often very irregular. They are about 25 — 30^ long. This species has been found in several places in the sound between St. Jan and St. Thomas in depth down to 30 — 40 meters. Geogr. Distrib. : Mediterranean Sea, warmer parts of the Atlantic Ocean, Canary Island, West Indies etc. ^g- Grateloupia C. As 1. Grateloupia filicina (Wulf.) Ag. Agardh, C, Spec. Alg., p. 223; Systema, p. 241. Greville, Alg. Brit, p. 151, pi. 16. Harvey, Phycol. Brit., pi. G. Kützing, Tab. Phycol., vol. XVII, pi. 22. J. Agardh, Spec. II, p. 180; Epicr. p. 153. Fucus filicinus Wulf, in Jacquin, Collectanea, vol. Ill, 1789, p. 157, tab. 15, fig. 2. Turner, Hist. Fucorum, pi. 150. Esper, Icones Fucorum, pi. 67. Grateloupia filicina is a littoral alga which commonly grows in more sheltered places in quite shallow water. Bertholü^) points out that most of the species of Grateloupia found in the Gulf of Naples were found in water polluted from the town. In such places Grateloupia filicina also occurs in the West Indies but furthermore it is much common in quite clear water and as it is often fixed to small stones scattered upon the dazzling white coral sand it grows in very intense light. In such places 1) Berthold, G., Die Cryptonemiaceen des Golfes von Neapel (Fauna und Flora des Golfes von Neapel, XII Monographie, 1884). 124 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. the plant assumes an often quite bluish-green colour while in places more protected against the light its colour is a dark red- brown or red-violet; by drying the blue-green specimens assume mostly a dark red-brown colour. The ramification is monopodial. It is a very variable plant ; in some specimens the branches are long in others short, in some the length of the branches grow evenly shorter upwards in others they are longer and more vigorous upwards and much ramified. Some specimens have a proportionally broad thallus in others the filaments are nearly thread-like. In some specimens the main filament bears along its whole length rather short un- divided branches. Kützing has figured several of these forms in his Tabulæ Phycologicæ. A transverse section shows the structure commonly found in Grateloupia. The medullary layer is very loose in the middle, denser towards the periphery where it goes rather evenly over into the cortical layer. The filaments in the medullary layer are about S fx thick; they are irregularly subdichotomously ramified and felted between each other. The cortical layer consists of short closely packed filaments whose innermost cells are nearly spherical, oblong to subcylindric at the periphery. The tetraspores are formed in great numbers over the whole thallus in the cortical layer; they are cruciately divided. The antheridia and cystocarps occur in the same plant as pointed out by Berthold. The antheridia are formed of the peripheral cells in the cortical layer as a kind of outgrowth from these; the spermatia are small spherical bodies about 4 — 5 [i in diameter. The cystocarps occur more or less over the whole surface of the thallus. They are spherical bodies about 180 /j. in diameter and reach far into the medullary tissue. The wall is well developed formed by filaments growing out from the auxiliary cell filaments. The cystocarps discharge by means of a pore through the cor- tical layer. The carpospores are densely crowded together forming a nearly spherical body. They are about 18 — 20 // in diameter. With the exception of the most exposed locaHties tliis species is com- mon along the shores of the Danish Isles. Geogr. Distrib.: Seems to occur in all warmer seas. 2. Grateloupia dichotoma J. Ag. J.Agardh, Algæ mar. Mediterr., 1842, p. 103. Kützing, Spec. Alg., p. 732; Tabulæ Phycologicæ, vol. XVII, tab. 28, figs, c — e. J. Agardh, Epicr., p. 152. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 125 As to their outer habit the specimens found show much hke- ness to the figures c and d of Kützing quoted above. A transverse section (Fig. 133) of the thalkis reveals the fact that the medullary tissue is very loose and open in the middle more dense outwards. It consists of thin cylindric filaments very irregularly, often stellately, branched and woven together. Their diameter is variable, often 5 — 6 [x thick. Towards the periphery they grow tkicker and mostly run more or less parallel with the surface of the thallus. From these filaments the cortical layer arises. This consists of short dichotomously ramified filaments placed verti- cally upon the surface of the thallus. The innermost cells in this layer are largest, nearly spherical, about 6/i thick; from these is an even transition to the peripheral ones which are subcylindric about 4/z thick and %n long. The tetraspores are found in great numbers in the cortical layer over the whole surface of the thal- lus. They are cruciately divided and about 27// long and 14// broad. The cystocarps occur scattered, more or less, over the whole surface of the plant. They are nearly sphe- rical about 180/« broad; the cells in the wall are of very irregular shape. The carpospores are formed in great quantities and are about 14// broad. This species is httoral; it occurs in quite shallow water in rather exposed places where it is dashed by the waves. Like Gr. cuneifolia it is found abundantly in polluted water near the town but it is also found in quite clear water. St. Thomas: The Harbour near Charlotte Amalie, the Hurrican Island. Geogr. Distrib. : Mediterranean sea, warmer parts of the Atlantic Ocean. 3. Grateloupia cuneifolia J. Ag. Agardh, J., Algologiska bidrag in Öfversigt k. sv.Vetensk.-Akad. For- handl. 1849, p. 85; Spec. Alg., vol. II, p. 181; Epicrisis, p. 164. Montagne, Sylloge gen. spec. Cryptog., p, 433. Kützing, Tab. PhycoL, vol. 17, tab. 34. Fig. 183. Grateloupia dichotoma J. Ag. Transverse section of the thallus with tetrasporangia. (About 550 : 1). 126 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. This species is a marked littoral alga. It grows together with Ulva etc. near the surface of the sea in places where the waves constantly dash the rocks. The thallus is tough and elastic with a glabrous and lubricous surface, very apt to grow in such localities. The specimens collected (comp. Fig. 134) reach a length of up to 40 cm and more. They are fastened to the substratum by means of a small disc. Immediately above this the thallus is terete but it soon be- comes compressed and passes evenly into the ribbon -like or leaf - like frond. This differs very much in shape, sometimes it is more narrow, sometimes broa- der i) ; some specimens are not divided at all but this is rare; most of the specimens are more or less lacerated or what is more common bear numerous smaller and larger pro- liferations along the margin. Towards the summit the thallus itself and the proliferations are evenly narrowed and run out often into long thin prolongations. The margin of the whole frond is more or less undulated. The colour is a deep red-violet. Kützing's above quoted figure seems to me to give a fairly good illustration of the plant. A transverse section (Fig. 135) of the thallus shows that a marked difference between the medullary tissue and the cortical layer is present. The medullary tissue consists of more or less cylindrical much .Fig. 134. Grateloupia cuneifolia J. Ag. A smaller much divided plant. (About half natural size). 1) The broadest specimens in my collection are 4 — 5 cm broad. F. Børgesen: Rhodophyceæ of the D.anish W. Indies. 127 Fig. 135. Grateloupia cuneifolia J. Ag. Transverse section of the thallus with tetrasporangia. (About 550 : 1). ramified filaments running between each other in all directions in the mucilage found here. In a longitudinal section it is seen that the medullary cells are very irregularly branched often more or less starlike (Fig. 136); the breadth of the cells is also very vari- able and this is also the case regarding the length of the cells. The develop- ment of these starlike cells is just the same as is de- scribed by Berthold (1. c, p. 2) for Halymenia. The filaments having got some length swell at the end and from this thickened part filaments grow out in all directions ; the ends of some of these filaments meet other similar ones and fuse together with them or their ends swell and give rise to new star-like cells. The cortical layer is composed of short dichoto- mously ramified filament;?. The innermost cells in these are the largest and more irregularly shaped, the outermost small oval to subcylindrical 8 — 9 /i long and about 3 // broad and rather closely packed together. The tetrasporangia (Fig. 135) are formed in the cortical layer and occur scattered over the whole surface of the thallus. They are cruciately divided about 30;/ long and 19 fi broad. Among the dried specimens a single cystocarpic one was found. While the tetrasporic specimens have quite a smooth sur- Fig. 136. Grateloupia cuneifolia J. Ag. Star-like cells from the medullary layer. (About 250:1). 128 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. face the female plant has a very uneven warty surface. The cystocarps are found spread over the whole thallus; they are placed rather deep in the medullary tissue, are nearly spherical and open by means of a pore through the cortical layer. Plants with tetraspores and cystocarps were met with in the months December to March. This species has only been found in very polluted water at the town Charlotte Amalie. St. Thomas: The harbour. Geogr. Distrib.: West Indies. Fam. 2. BhizophyUidaceæ, By Mme A. Weber-van Bosse. Contarinia Zanardini. 1. Contarinia Magdæ nov. spec. Thallus totus substrato adhærens, ad basin calcareus, con- stans hypothallo et perithallo. Hypothallus constat fihs ramosis, parva flabella efficientibus. Perithallus constat filis erectis, dicho- tomis, quorum cellulæ peripheriam versus decrescunt. Cellulæ altæ 40, 20, 12 «, latæ 20, 16, 12 a. Tetrasporangia in soris ex apice fili transformata, clavato- obovata, irregulariter cruciatim divisa; alta 36, 40 /i, lata 16, 20/^. Contarinia Magdæ^) is the first alga of this genus collected in the West Indies were it was gathered by Dr. Th. Mortensen in the "Sound" between St. Thomas and St. Jan. It is growing on and entirely enveloping a hard mass of small stones and coral that had a diameter of 3 cm. Of its colour it is impossible to judge for the spe- cimen is preserved in alcohol. It is distinguished from C. Peyssonne- liæjormis by its frond, calcified at the base and only free from carbonate of lime in its upper part, whereas the whole frond of C. Peijssonneliæjormis is fleshy (carnosa). The size of the cells shows another difference between the two algæ: the cells of C. Magdæ have a breadth of rarely 40, mostly 20 //, at the base, diminishing towards the periphery wehere they measure often 20 and even 16 and 12//. The height of the cells at the base and the middle of the filament is sometimes 2 — mostly IV2 as high 1) So called in honour of Mrs. Borgesen, the graceful wife and compa- nion of the explorer of the Danish West-Indian islands. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 129 oQ9999HD\100Dnnr mm 000 Mal as broad or isodiametric ; towards the periphery the cells are, as a rule, as high as broad or a little less. Seen from above the peripheral cells have a diameter of d= 20 /m. The cells of C. Peys- sonneliæjormis have a breadth of 20 — 12 fj. at the base, lessening upwards to 8 and io b fi sX the top ; they are from IV2 to 4 times as high as broad. The vertical rows of cells of C. Magdæ loosen themselves from each other under very slight pressure after decalcification and only their basal cells remain fastened together. This will probably be in consequence of the disappearance of the carbonate of lime. There are lateral pores be- tween the cellrows, but the pores are very delicate and do not tend to make the frond much firmer. C. Peyssonneliæjormis has no carbo- nate of lime between its cellrows, which do not loosen themselves from each other under slight pressure ; the frond is soft and fleshy to the touch after having been moistened. The tetraspores of C. Magdæ are born in sori at the top of the vertical cell-rows (Fig. 137); they divide in a cruciate way, but the divisions are often irregular and sporangia with two and three spores only, are not rare. They are covered by a pretty firm cuticula, that seems to tear off at maturity of the spores. The sporangia have a height of 36- 16—20 jji. ODOn&SnW DO DDL Dato. Fig. 137. Contarinia Magdæ n. sp. a. section through vege- tative part of tliallus in full growth, with the cells in the higher part dividing repeatedly. b. section through part of a soruswith tetrasporangia at the top of the filaments. (120:1). -40 fx and a breadth of Found in the "Sound" between St. Thomas and St. Jan by Dr. Mortensen. Fa/77. 3. Squamariacece» By Mme A. Weber-van Bosse. When treating of the Squamariaceæ of the "Sealark" expedition, I divided the Peyssonnelia into three subgenera: 1. Peyssonnelia s. s. or Eupeyssonnelia with a hypothallus consisting in the main of straight filaments, running close to one another in a horizontal Dansk Botanisk Arkiv, Bd. 3. Nr. 1. (1916). 9 130 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 138. Peyssonnoliä simuläns n.SY). Straight running filaments of the hypothallus. (160:1). direction over the substratum (Fig. 138), 2. Cruoriella with a hypothallus of curved filaments running in little fan-shaped or broad-lanceolate groups over the substra- tum (Fig. 139) and 3. Ethelia with no hypothallus but a mesothallus that gives off branches both downward and upward. This division proved very useful while working out the Peyssonnelia of Dr. Bør- gesen. In his collection species of Peys- sonnelia and Cruoriella are numerous but the subgenus Ethelia is wanting, it has till now been only found in the East- Indian seas and in the Mediterranean. P. sqiiamaria, the well-known inhabitant of the last-named sea, has a true mesothal- lus though the perithallus inferior is re- duced to only one layer of cells. It is a well-known fact that algæ have a great variability and in how far the Peyssonnelia are subject to this general law, is still an open question, for this group of plants has relatively been little studied. We know that the circular or lobed fronds can be membranaceous (P. rubra), coriaceous (P. sqiiamaria), or calcareous and hard as stone (P. polymorpha), but there are also other forms not entirely calcareous neither coriaceous ; we will have to speak of such a species in the following pages. A frond will, as a rule, increase in thickness by successive division of its ascending filaments, but in the group of P. (Cruoriella) polystrata we find a thick frond consisting of layers of nar- row fronds lying one above the other, creeping continually over each other and forming a thick frond by this mode of growing. Again in another species the frond, after having acquired a certain thickness, splits or tears in a horizontal direction ; the lower part decays little by httle, the upper part continues the growth of the frond ; its in- ferior cells grow larger, produce rhizines and develop the characters of an ordinary hypothallus. Such a young thallus, after having ac- quired the necessary thickness, will split in its turn ; I have seen Fig. 139. Cruoriella armo- rica. Crn. Filaments of the hypothallus forming little fanshaped groups. (90 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 131 two and three remnants of old thalii underlying a young one. It is curious that the old thalii decay in this species, whereas in P. (C.) dura — the type of Heydrich's Polystrata — all the thalh are preserved. This depends, as I believe, on the fact that P. (C.) dura has a calcareous frond and that P. (C.) Nordstedtii, as we will presently see, is mostly of soft texture with only little calcareous matter distributed throughout the frond. The anatomical structure of the Peyssonneliæ is much alike; it consists, as we know, of creeping fdaments — the hypothallus — and each cell of these filaments gives ofT, seen on longitu- dinal sections, an obliquely ascending filament, these constitute the perithallus. The cells of the perithallus differ in heigth and breadth in different species, but still these characters are to be used very carefully, for the size of the cells will vary in the same specimen according to the spot where the section is made and according to the age of the plants. On the other hand, when studying many species of this genus, we find different species with cells of almost the same size. Searching for a character that might help to distinguish the puzzling species, I was struck with the fact that the topcell or apical cell divided difTerently in some species, though these divisions corresponded essentially with the divisions of P. (Eup.) squamaria. The anatomical structure of this alga has been, as we well know, the object of careful research by Naegeli^), who has also given good figures to show, how the filaments of the hypothallus, seen from above, divide dichotomously to increase their number, according to the fan-shaped growth of the frond. The longitudinal growth of the filament that interests us for the present, depends upon the partition of the apical cell by a more or less oblique membrane on its longitudinal axis. In P. (Eup.) squamaria and — as far as I can judge — in most species, this apical cell is relatively high (in vertical direction) and horizontally short. After division, the outermost segment grows on, until it has reached its former size and then divides again. The inner segment increases also in size, it may divide again by a vertical cellwall, though this is rarely the case; as a rule it divides, after having attained a given size, by a hori- zontal wall into two unequal portions of which the uppermost is destined to become the mothercell of the ascending filament and the inferior constitutes part of the hypothallus. This inferior cell may be less high than the superior one {P. (Eup.) squamaria) or 1) Nakgeli, Die neueren Algensysteme, 1847, p. 248. 132 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig.- 140. Peyssonnelia (Cru- oriella) simulans nov. spec. Section throug tlie margin of thailus. t. topcell or apical cell ; the one row of inferior cells constitute the hypothal- lus, the ascending, still short cellrows, the perithallus. (200:1). it may be higher {P. (Eup.) simulans), but it is always less high than the apical cell (Fig. 140). In a few other species {P. (Eup.) rubra) the topcell or the cells following may be longer than high ; it divides just like the short one by an oblique cellwall on its longitu- dinal axis into two segments. The outer one grows until it has reached its for- mer size and then divides again. The in- ner segment will grow too, and may first divide again by a vertical cellwall ; if this is the case, the third or even the fourth cell after repeated division, increases in height and then divides by a hori- zontal wall into two often unequal portions. The inferior one retains the height it had at the moment of divi- sion of the apical cell; it communicates with its neighbouring hypothallic cells of the same filament through the primary cen- tral pore ; the upper portion is the mother cell of the ascending filaments. I thought at first that these differences in growth oi the apical cell might coincide with the branching of the hypo- thallus, but this is not the case. I have found the short, high apical cell in species belonging to the subgenus Eupeyssonnelia as well as to the subgenus Cruoriella and in both subgenera the longer and less high apical cell. Therefore I consider this character only useful as a specific one, but as a good one, for great as the va- riability of the Peyssonnelia may be, I can not imagine that a top- cell as in Fig. 140 can grow into a topcell like Fig. 144. When treating of the Peys- sonnelia of the Siboga Expedition, I hope to be able to give some more details about the growth of the apical part of these algæ, but this study is very tedious, for dried specimens have the margin often crumpled or broken off. It is also difficult to get good longitudinal sections and the topcell must be in a growing stage. In old fronds, when their maximum size is reached, the topcells cease growing in radial di- rection but they may still divide in another way and slides made Fig 141. Peyssonnelia rubra {Gve\.) J. Ag. A longitudinal section through margin of thallus. t. top- cell; p. perithallus; h. hvpothal- lus; rh. rhizoid. (360:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 133 unfortunately through a thallus in such a state, will only add to the confusion. ^) The fruit of the Peyssonnelia are nemathecia with carpo- spores and tetraspores raised above the surface of the frond. By these nemathecia the Sqiiamariaceæ are easily known from the Melobesiaceæ which they resemble so much in anatomical structure. Scidiitz^) described the development of the procarp and the auxiliary cells in Peijssofinelia but he gave no figures and it is highly desirable that his investigations should be re- peated. It is, however, very difficult to obtain good material. The collection of Dr. Børgesen contains only nemathecia with carpospores and tetraspores. But nemathecia with ripe carpo- or tetraspores are also a character of importance when describing new species. While stu- dying the Siboga material I had ample occassion to appreciate their value, but the specimens collected by Dr. Børgesen are more uniform in this respect than the East-Indian species. The collection of Dr. Børgesen is rich in Peijssonnelia. Maze et Schramm in their "Les Algues de la Guadeloupe" mention only Peijssonnelia Diihyi and Murray in his "Catalogue of marine algæ of the West-Indian region" knows of no other representative of this family. It is therefore not strange that Dr. Børgesen's collection contains many novelties but, alas, also some plants about which I feel uncertain. These algæ resemble well-known species but are not exactly hke the type-specimens; if now the 1) Continuing my research on the apical cell of the Peyssonnelia after having finished this paper, I observed a stage of rest in the thallus of P. rubra, followed by a period of intense growth. A section through the margin in a state of rest, gave a figure resembUng the figure of P. Boergesenii (Fig. 144). On this period of rest followed a period of growth in which the topcell and the cells immediately following it, wore difTereht aspects in succeeding longitudinal sections. I think that these succeeding stages of growth and rest correspond with the con- centric lines and smooth zones we observe in the thallus of P. rubra that has, as we know, a turned up margin. The spot from where the new growth begins, is attached by rhizoids to the substratum; the young frond curves distinctly upwards but by succeeding growth it stretches itself horizontally and will afterwards attach itself to the substratum. I suppose that the concentric lines on the thallus coincide with the spot from where the new growth begins, and which carries many rhizoids. The intervening zones between two concentric lines have as a rule far lesser rhizoids. 2) Schmitz, Untersuchungen über die Fruchtbildung der Squamarieen, Sitzungsber. d. niederrh. Gesell. Bonn, 1879, p. 376. 134 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. material was scanty or the specimen sterile, I queried these doubtful specimens and placed them near to the species which they most resemble, leaving it to future investigators to decide whether they are forms of the type — or new species. One specimen belongs probably to the genus Criioriopsis, but it is in such incomplete state, that it cannot be identified with certainty. Besides the easily known and doubtful species the collection of Dr. Børgesen contains: two new Cruoriella, one new Peyssomielia and one new Contarinia, of the family of the Rhizophyllidaceæ. Before giving the systematic Hst of the species, 1 may per- haps add a few words to express my sincere thanks to Dr. Bør- gesen, for entrusting me with his collection and to Mr. Ha.riot of the Museum d'Histoire Naturelle de Paris, for his kind help in sending me valuable specimens for comparison. Cruoriopsis Dufour. 1. Cruoriopsis spec. One of the small specimens in the collection of Dr. Børgesen carries at the top of the ascending filaments two short files of moniliform cells of peculiar aspect; they remind one of the car- pospores in the cystocarps of Cruoriopsis cruciata. The cells are, however, still very young and I have seen no other organs of fructification. I do not dare to name this alga with certainty but I think it likely, that it is a member of the genus Cruo- riopsis. Found at St. Thomas, in the harbour at the French Wharf. (N. 52). Dry Specimen. Peyssonnelia Dec. Key to the subgenera and species of Peyssonnelia from the West-Indian region, collected by Dr. F. Børgesen. I, Thallus procumbent, more or less firmly adhering to the substratum, orbicular or irregular in outline, with a hypothallus consisting of dichotomous filaments, run- ning from the centre towards the periphery and form- F. Børgesen : Rhodophyceæ of the Danish W. Indies. 135 ing small, lanceolate, fan-shaped groups. From the cells of the hypothallus rise more or less obliquely ascending filaments: the perithallus. . . Subgenus Cruoriella. a. Thallus hard, calcareous, firmly adhering to the substratum. 1. Thallus very thin, when decalcified easily de- tached from substratum and so small that it can be expanded in toto on a slide ; colour dark pink. P. armorica Grn. 2. Thallus much firmer, surface slightly marked with small low elevations, sometimes with radial lines but no veins; perithallus with an inferior part of large cells and a distinct superior part with small cells ; colour dark pink . . . P. Duhiji Crn. 3. Thallus very firm, surface smooth but with di- stinct veins running from the centre towards the periphery ; perithallus with cells often almost isodiametric except the basal large and the su- perior small ones. Colour dark purple with a green hue P- Boergesenii nov. spec. b. Thallus fleshy, slightly calcareous at base, firmly adhering to substratum and tearing in horizontal direction after having acquired a given thickness. Inferior cells of the upper, torn off, part transform into a new hypothallus ; colour probably pink . . . P. Nordstedtii nov. sp. II. Thallus procumbent, adhering more or less firmly to the substratum, orbicular or irregular in outline, with a hypothallus consisting of in the main straight, juxtapposed, dichotomous filaments, running from the centre towards the periphery, giving rise to more or less obliquely ascending filaments: the peri- thallus Subgenus Eiipeyssonnelia. a. Thallus hard, calcareous, with short, high apical cell. 1. Thallus thin, consisting of 6, 7 layers of cells, easily detached from substratum, mostly orbi- cular with radial lines; colour light pink .... P. simulans nov. sp. 2. Thallus more robust, firmly adhering to the substratum, colour purple P. conchicola Pice, et Grun. 136 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 3. Thailus very firm, easily loosened from the sub- stratum, irregular in form; perithallus with in- ferior part of large cells, superior part with smaller cells; colour brick red P. polymorpha (Zan.) Schm. b, Thallus membranaceous-calcareous with long apical cell as high as hypothallic cells, orbicular with shght radial lines and concentric zones; colour pink or red. P. rubra. Subgenus 1. Cruoriella Cm. 1. Peyssonnelia (Cruoriella) armorica (Cm.). Cruoriella armorica Crouan in Ann. Sc. Nat., 1859, 4e serie. t. 12; Flor. du Finist. 1867, p. 148, tab. 19, fig. 128. De Toni, Syll. Alg. vol. IV, 1905, p. 1691. This small alga was detected growing on other Peyssonnelia. Thanks to the extreme kindness of M. Hariot, assistant au Mu- seum d'Histoire Naturelle at Paris, I was able to compare it to an authentic specimen of Crouan. The comparison showed the absolute identity of the two specimens. Found at St. Thomas in the sea to the v^^est of Water Island in a depth of about 15 fathoms. In alcohol. (No. lllOni). Geogr. Distrib.: Atlantic coast of Europe, Mediterranean Sea. 2. Peyssonnelia (Cruoriella) Dubyi Cm. Crouan, Ann. d. Sc. Nat. 1844, p. 368, tab. 11. Schmitz, Uebers. der Florideen, 1889. p. 20. De Toni, Syh. Alg. vol. IV, sect. IV, 1905, p. 1691. Peyssonnelia Dubyi belongs to the subgenus Cruoriella because its hypothallus consists of fan-shaped little groups of filaments. These filaments have in horizontal direction a short and in ver- tical direction a high apical cell, higher than the cells in the hypothallic filaments. P. Dubyi was the only known Squamariacea of the West- Indian region before Dr. Borgesen's Expedition. Found at St. Thomas in the sea to the west of Water Island in a depth of 15 fathoms. (N. 1030). Dry specimen. Geogr. Distrib.: Atlantic coast of Europe. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 13^ I 3. Peyssonnelia (Cruoriella) Boergesenii nov. spec. Thallus totus adnatiis, valde calcarius, superficie levi cum singulis venis conspicuis, e centro ad peripheriam currentibus, constans hypothallo et perithallo. Hypothallus constat filamentis repentibus, juxtappositis, flabella angusta, elongata, efficientibus. Cellula apicalis longa; cellulæ filamentorum hypothalli æque altæ aut altiores ac cellulæ apicales. In speciminis juvenilibus omnes cellulæ filamentorum repen- tium fere æquales, in speciminis adultioribus axis principalis con- spicuus, cellulis majoribus. Perithallus divisus in partem inferiorem, cellulis magnis, tetragonis aut IV2 altioribus quam latis, altis 40—36 /^, latis 40— 36 — 20 fi et in partem superiorem, cellulis gradatim decrescentibus. Cellulis periphericis multo brevi- oribus quam latis, altis 10 //, latis 20 f A. Nemathecia cum carposporis quadripartitis zonatis, paraphyses cellulis longioribus quam latis, altis 40—36—16-12 fjt, latis 6—8— 12/7. et cellulis apicalibus monili- formibus. Nemathecia cum tetra- sporangiis ignota. Thallus altus ± 500 //, nemathecia 240 /^. Peyssonnelia (Cruoriella) Boer- gesenii^) (Fig. 142) distinguishes itself by its smooth surface marked with delicate but distinct veins, visible to the naked eye and running in a fan-shaped di- rection from the centre towards the periphery. These veins are quite different from the radial lines, we observe f. i. in the thal- lus of P. rubra and depend probably upon the axis with large cells of the hypothallus. In a dried state the colour of the thal- lus is very striking owing to the greenish hue of the dark purple frond. In the collection of Dr. BørCxESEN are four numbers from the same locality that I believe belong to this species, though in structure they show some differences, but these differences depend on the age of the individuals. Seen from below No. 1442 Fig. 142. Peysonnelia Boergesenii nov. spec. Surface view of the plant. X 1,6. 1) I have great pleasure in dedicating this alga to Dr. Børgesen, the botanist and explorer of the marine flora of the Danish West-Indies. 138 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. has a hypothallus with cells of the same size, whereas No. 1546^-^ seen from below, has a hypothallus with cells of different size constituting a principal axis of larger cells from which spring files of smaller cells, that form together groups, like elongated little fans. The frond of No. 1546" is rather thick, it must be an old plant and I think that by succeeding growth, changes in the basal layer of the frond have taken place. Only too often, when stu- dying Peyssonnelia , one sees that the basal layer undergoes changes, and these can ultimately tend to the solution and even disappearance of part of the hypothallus. In P. Boergesenii the mmp- n wwmm- Fig. 143. Peyssonnelia Boergesenii nov. spec. View of two hypothalli, loo- sened from the substratum, a. (No. 1442) young hypothallus. principal axis not yet differentiated, b. old hvpothallus with distinct principal axis. (No. 154611). (210:1). hypothallus is not soluted ; the cells of the principal axis increase simply in size. The apical cells is long and as high as or less high than the cells of the basal layer (Fig. 144) '^) and in this respect P. Boerge- senii differs from P. Nordstediii that has a high, short apical cell, like Fig. 140. The perithallus (Fig. 145) consists of a lower part of almost square cells, high d=40//, on which follows an upper part with 1) The section after which this figure was made, did not quite satisfy me; I fear that it is a section throug a margin no longer in a grow- ing state, but I could get no better for the margin of the alga was very much broken off. This section shows, however, that the apical cell is not a high, short one. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 139 Fig. 144. Peyssonnelia Boergesenii no v. spec. Section through dried margin of thallus. t. topcell. (380 : 1). cells higher than broad, di- minishing regularly towards the periphery, the peripheral ones being the shortest of all: height 10 fi, breadth 20«. This succession is, however, not always so striking as told here. The frond can easily attain a thickness of 500//, even more, for my sections do not run through the thickest part of the frond. The cells contain much gra- nules, that take at first a golden brown colour by hydrochloric zink- iodine and become almost black under long influence of the reagens. I have only seen one nemathecium with carpospores. It had a darker colour than the frond, was ele- vated above its sur- face and irregular in form ; it had a height of 240 /i and the qua- dripartite, zonate car- pospores of IQOfjt, but these looked as if they were not yet quite ripe. The paraphyses ended in a short, round cell, not in a broad blunt one (Fig. 145, a). Nemathecia with antheridia were more frequent ; I found them on the same plant as the carpo- spores (Fig. 145 c). This Peyssonnelia resembles P. Harvey- ana very much with røDfl Fig. 14.5. Peyssonnelia Boergesenii nov. spec. a. section through nemathecium with carpo- spores ; b. section through thallus in transverse direction; the inferior cells are sometimes larger when the section hits upon a principal axis of the hvpothallus; when the section is made in longitudinal direction the inferior cells ascend obliquely. (250 : 1). c. section through nemathe- cium with antheridia. (540:1). 140 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. regard to its anatomical structure, but it difTers from this alga by its hypothallic filaments, running in little flabelliform groups over the substratum; the colour of both algæ is also different, P. Boergesenli being of a dark purple colour with a greenish hue over it, P. Harvey- ana of a bright red colour. Lastly P. Boergesenii is also character- ized by the distinct veins running from the centre towards the periphery. Found in shallow water, St. Croix, White Bay. (N. 1537 n, 1546 n, 168511). Rust of Twist (N. 1442). In alcohol and dry specimens. 4. Peyssonnelia (Cruoriella) Nordstedtii nov. spec. Thallus tota superficie inferiore adhærens, paulum calcarius, colore ignota, diametro usque ad 4 centimetrum, constans hypo- thallo et perithallo. Hypothallus constat filis repentibus, juxtap- positis, parva flabella efficientibus. Cellula apicalis fdorum alta et brevis, in sectione longitudinali altior filis hypothalli. Cellulæ longæ 28—36—40^, latæ 16—20—28,« et ± 28// altæ. Perithallus constat filis adscendentibus, stratum satis crassum, denique fissum formantibus. Pars inferior hujus strati peril, pars superior hypothallum novum efficit, cum radiculus uni- et pluri- cellularibus partem inferiorem tegente, radiculis iis in partem in- feriorem penetrantibus. Cellulæ altæ ± 12—20—36 u, latæ 12—16—20/^. Nemathecia cum tetrasporis quadripartitis, cruciatis, tantum immatura visa. Peyssonnelia (Cruoriella) Nordstedtii^) resembles an alga col- lected at the island of Nias, Sumatra, that I have called in my manuscript of the Siboga-algæ, later on to be published, P. Nord- stedtii. Both algæ have in common a frond of soft texture, only slightly incrustated with carbonate of lime and the peculiar way of renovating the frond. P. Nordstedtii belongs to the subgenus Cruoriella on account of its hypothallus consisting of filaments branching by repeated dicho- tomy, which branches grow until other filaments, crossing their way, stop their growth. The branching filaments form little elongated fan-shaped groups, springing from a principal axis with larger cells than the cells in the fan-shaped groups, just like what we have seen in P. Boergesenii (Fig. 143). Characteristic of P. Nordstedtii is the way in which the peri- 1) Named in honour of and in gratitude to Prof. O. Nordstedt at Lund, the learned algologist, to whom I owe so many graceful acts of kind- ness. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 141 thallus may tear horizontally after having acquired a thickness of 11 cells or more. The inferior 4 — 5 cells are the largest, the cells higher up are smaller in diameter, and the peripheral cells are the shortest of all. Between the inferior large cells and the succeeding ones, which are somewhat smaller, the membrane thickens. This thicke- ning of the membrane takes place in horizontal direction, and may spread over some distance. In this thick membrane ap- pears at first a slight opening, this enlarges, tears the membrane horizontally and divides the perithallus into a superior and inferior part; these can remain jointed but very often they tear asunder. Fig. 146. Peyssonnelia Nordstedtii nov. spec. Section through thallus in transverse direction in the moment that the upper part tears itself from the partially decaying inferior part. (210 : 1). In either case the upper part will increase in thickness and its inferior cells increase in size, and then the membrane will again thicken at the same place as formerly, above the four or five layers of large cells. If the perithallus is not torn, we see the succeeding layers forming one continuous mass. But often the perithallus splits into two layers; if this hap- pens we observe first a little opening in the thickened membrane, this enlarges quickly and divides the perithallus into two parts (Fig. 146). The upper part transforms its basal cells, that were formerly in the middle of the ascending filament, into a young hypothallus, with uni- and pluricellular rhizines that penetrate in the inferior part of the perithallus. 142 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The cells of this inferior part are filled with grams of starch, yet they will die or dissolve little by little; it may also be that the rhizines get some nourishment out of them. In sections I have often seen three layers of thalli one above another. By these superposed thalh P. Nordstedtii approaches the group of P. polystrata of which P. dura Heydr. is the type. The name dura, given on account of the hard calcified nature of the frond, is alone sufficient to show that our alga with its soft frond, is a different species, not to speak of other differences, afforded by the peculiar structure of the nemathecium of P. dura. I have seen only one nemathecium of P. Nordstedtii with cruciate tetraspores, but it was still unripe. It had a height of 80^, and the paraphyses ended with a blunt cell; the cells were 1^/2 — 2 as long as broad but this will change with succeed- ing growth. P. Nordstedtii ad- heres totally and firmly to the sub- stratum. I cannot say anything about its colour for it was preserved in alcohol and I have seen no dry specimens from the W. Indies. The specimen from Nias that has so much in common with the W. Indian one, has a pale pink colour. Found at St. Jan off Cruz Bay in a depth of about 12 fathoms. In alcohol. (No. 1903). Fig. 147. Peijssonnelia Nordstedtii nov. spec. Sec- tion through part of nemathecium with cruciate tetraspores. (250 : 1). Subgenus 2. Eitpeyssofifielia. 5. Peyssonnelia (Eupcyssonnelia) simulans nov. spec. Thallus tenuis, orbicularis aut irregularis, substrato tomento brevi adhærens sed facile a substrato solutus, durus, calcarius, zonas concentricas et lineas radiales vix conspicuas exhibens, con- stans hypothallo et perithallo. Hypothallus constat fills rectis, juxtappositis, cellula apicali brevi, lata instructis. Cellula apicalis in sectione radiali altior fibs hypothalli. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 143 Cellulæ longæ 20—28—32—40/7, latæ 16—20//, in sectione altæ 20—24//. Perithalli cellulæ infimæ omnes fere æque altæ ae cellulæ hypothalli ; in sectione transversali altiores quam latæ, in sectione longitudinali fere quadraticæ, cellulæ superiores gradatim de- crescentes. Cellulæ altæ 24— 28 /i, latæ 20^. Nemathecia in thallo parvas maculas obscuras irreguläres ef- ficiunt, carposporis tripartitis zonatis et paraphysibus obtusatis quorum cellulæ IV2 altiores sunt quam latæ. Nemathecia alta 200 fj.. Carposporæ 100 /i. Nemathecia cum tetrasporangiis, cruciatim divisis. Tetrasporæ altæ 60 — 80^. Peyssonnelia simulans has received its name because it has so many points in common with P. conchicola that I felt doubtful, whether it might not be a form of P. conchicola but it can not be identified with this alga and therefore I prefer to describe it as a new species. P. simulans distinguishes itself from P. conchicola by adhering loosely to the substratum; the collection of Dr. Børgesen con- tains entire loosened specimens, whereas P. conchicola adheres firmly to the substratum. The colour is different in both algæ, P. simulans being of a bright pink colour — not red — and P. conchicola of a red colour that fades partially away in drying. The faded parts have a yellowish pink colour. It is true that as a rule colour is a bad characteristic of algæ but in the Peyssonnelia it is such a marked feature, that it probably can be of great help in knowing the different species. P. simulans resembles P. conchicola by its hypothallus con- sisting of straight-running filaments ending in a short, high apical cell, which is higher than the filaments are at a little distance from the top. Its perithallus is characterized by an almost square lower cell, that divides at its top, seen in longitudinal section, in two rows of cells (Fig. 140). This is often the case in species of Peyssonnelia but seldom so regularly and in such a marked way as in this species. Under slight pressure on the covei: slip, the cellrows loosen in vertical direction after decalcification and this I have never observed in sections of P. conchicola. I could study this alga thoroughly thanks to the kindness of Dr. A. Forti, who send me an authentic specimen of Dr. Piccone for compari- son. I may well thank him here for his kindness. The thallus of P. simulans is incrustated with carbonate of lime; it is thin, the thickest thallus in Dr. Børgesen's collection 144 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. has no more than five or six layers of cells and thalli with three layers of cells carried even nemathecia with tetraspores. A spe- cimen (No. 1110") preserved in alcohol, carried nemathecia with tripartite, zonate carpospores (Fig. 148); one layer of cells under the nemathecia was exceptionally high in another plant. Some plants have a thick basal layer of mucuous substance, but this character is not constant. To sum up the differences between P. simulans and conchi- cola we find that P. simulans has a lighter colour, does not ad- here to the substratum and that it must carry more carbonate of lime in its tissue for, after decalcification, the cells loosen easily from each other in vertical direction. The contents of the older cells, con- sisting principally of grains of starch in P. simulans are more ho- mogenous in P. conchi- cola. For all these rea- sons I am, I believe, authorized . to describe the present alga as a new species. ©liiiiiliiiliiif (ii®(S®©©i)®©®@iiii)C ®@®i)i)i)i§®ii©i@)0(ic Fig. 148. Peyssonnelia simulans nov. spec. Cross section through thallus with nemathe- cium with carpospores. b. basal layer of mucuous substance. (000 : 1). This species was found at St. Thomas in the sea to the west of Water Island in a depth of about 15 fa- thoms (No. lllOii), St. Jan off St. Cruz Bay in depths of about 10-15 fathoms (No. 1916, 1752, 1828), off Ram's Head at depth of about 25 fa- thoms (No. 1943). In alcohol and dry specimens. 6. Peyssonnelia (Eupeyssonnelia) conchieola Pice, et Grun.(?) PiccoNE etGRUNOw in Piccone, Algæ eritrea, 1884, p. 317. De Toni, Syll. Alg., vol. IV, sect. IV. 1900, p. 1700. The algæ from the West-Indies that I call P. conchieola, ad- here firmly to the substratum and resemble in anatomical char- acter the type specimen from the Red Sea. The West Indian ones carry nemathecia with tetraspores, nemathecia with carpo- spores I have never seen. P. conchieola has been described by Grunow and Piccone after barren specimens; it may therefore BOTANICAL OAKDt.N F. Børgesen: Rhodophyceæ of the Danish W. Indies. 145 be possible that, if fertile specimens are found, the West-Indian plant will prove to be a different species, I queried it therefore and also, because its colour is darker than the colour of P. con- chicola. It resembles, as already stated, P. conchicola in anato- mical structure and differs from P. simulans, in adhering firmly to the substratum. From P. rubra it is easily known by its long apical cell. Found at St. Croix, White Bay, in shallow water (No. 15371, 15461, 15851). In alcohol and dry specimens. Geogr. Distrib. : Red Sea. 7. Peyssonnelia (Eupeyssonnelia) polymorpha? (Zan.) Schm. Schmitz, in Falkenb., Alg. Neap., 1879, p. 264. De Toni, Syll. Alg., vol. IV, sect. IV, 1905. p. 1701. Lithymenia polymorpha Zanard., Icon. Phyc. Adriat. I, 1860, p. 127, tab. 30. % Fig. 149. Peyssonnelia con- chicola Pice, et Grun. Cross- section through nemathecia with tetraspores. (260:1). The specimen No. 1966 belongs probably to P. polymorpha, but it is too small to name it with certainty. It was collected with the dredge and we know that P. polymorpha prefers deeper water. M™^ Lp:moine ^) has de- scribed this alga from various locali- ties in the Mediterranean, and a va- riety of it has also been found at the island of Amirante^) The speci- men from St. Thomas has the typical brick-red colour of the species, the hollow crust is entirely loosened from the substra- tum and the anatomical structure is very much like that of P. polymorpha. The specimen bore nemathecia with unripe carpospores. Found at St. Thomas near the West-End of the island off Thatch Bay in a depth of about 14- 16 fathoms (No. 1966). Dry specimen (by Dr. Th. Mortensen). Geogr. Distrib.: Mediterranean Sea. 1) Mme p. Lemoine et M. Mouret, Sur une algue nouvelle pour la France. Bull. Soc. Bot. 1912, p. 356. ^) A. Weber-van Bosse, Rhodophyceæ of the "Sealark" Exp. Trans. Linn. Soc. 1913, p. 139. Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 10 146 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 8. Peyssonnelia (Eupeyssounelia) rubra (Grev.) J. Ag. J. Agardh, Spec. Alg. II, 1851, p. 502, Epicr. Flor. 1876, p. 386. De Toni, Syll. Alg. vol. IV, sect. IV, 1905, p. 1696. Zonaria rubra, Greville in Linnean Transact. XV, prt. 2, p. 340. After some hesitation I have named two specimens in Dr. Borgesen's collection as P. rubra, though Schmitz^) doubted of the occurrence of P. rubra in a tropical sea and though, according to J. Agardh, P. rubra should be limited to the Mediterranean. J. Agardh describes the frond of P. rubra as "membranacea" but the carbonate of lime incrustated between the rhizoids and in the basal mucuous layer makes the plant very brittle and calcareous. I could detect no difference between specimens from Naples, Genoa, Antibes and those from the West Indies. The latter are perhaps a little more delicate and orbicular, not so profoundly lobed as the Mediterranean species can be. Found at St. Croix, White Bay, shallow water, (No. 1546 n 1585 H). Dry specimens. Another specimen (No. 2034) found at St. Jan, off America Hill in a depth of about 15 fathoms, is distinguished by its light, pink colour and thin thallus from P. rubra. Its ascending filaments, seen in longitudinal direction, run more obliquely and the first cell of the perithallus is higher than is usually the case in P. rubra. This alga stands between P. rubra J. Ag. and P. Gunniana J. Ag. I hope that future explorers of the West- Indian region, with more material at their disposition, will shed further light on the systematic position of these confusing membranaceous species and will settle my doubts about P. simulans, whether it is a new species or to be sunk in P. conchicola. I felt, while working out this collection, that to know the limits of a species, one must first distinguish, in order to be able to unite afterwards and that for the present I could only distin- guish and had no right to unite. Fam. 4. Hildenbrandiaceæ. HildenbrandiaM Nardo. 1. Hildenbrandia prototypus Nardo. Nardo, I., in Isis, 1834, p. 675 [Hildbrandtia). Hauck, F., Meeres- algen, p. 38. 1) Schmitz, Marine Florideen von Deutsch Ost-Afrika, Engler's bot. Jahrb., 1895, p. 172. ^) Regarding the spelüng of the generic name compare the foot note in Engler u. Prantl., »Die Natiirl. Pflanzenfamihen« , I. Teil, Abt. 2, p. 544. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 147 Hildenbrandia Nardi Zanardini, Synopsis Algarum in Mari Adriatico hucusque collectarum (Acad. Re delle Sc. di Torino, Cl. mat. e fis., 2 ser., t. IV, p. 238, tab. 1, fig. 1). J. Agardh, Spec. Alg., II, p. 494, III, p. 379. H ildenbrandtia sanguinea Kütz., Phycologia generaUs, 1843, p. 384, tab. 78, V. This alga has been found in shallow water near the shore covering stones and pieces of rocks. I have compared my plants with European specimens from various places and they seem to agree quite well with these. The cells in the vertical rows of cells in the thallus are about 4 — b [x broad. Hauck 1. c. says that they are 4//. The irregularly shaped tetrasporangia are cruciately divided but often the walls are placed rather anomalously. The tetra- sporangia are about 25 /u long and 13 /^ broad. This plant occurred in more sheltered places. As I previously have mentioned ^) its thin purple-reddish crusts were found upon stones in a lagoon at St. Croix growing in the shade of the man- grove trees; at St. Jan it was growing upon small round stones in a more open place. St. Croix: Saltriver Lagoon. St. Jan: Cruz Bay. Geogr. Distrib. : Jamaica, Brazil, Atlantic Ocean, Mediterranean Sea, Pacific Ocean etc. most probably ubiquitous. Fam. 5. Corallinaceæ. Subfam. 1. Melobesieæ. Par Mme Paul Lemoine. L'importante collection de Mélobésiées recueillie par M. Boerge- SEN au cours de ses voyages aux Antilles Danoises avait été con- fiée å M. FosLiE, de Trondhjem, que la mort a surpris (1909) avant qu'il ait pu terminer son travail. II restait å determiner un certain nombre d'échantillons ; M. Boergesen a eu l'amabilité de m'en proposer l'étude. Quelques-unes des espéces déterminées par M. FosLiE étaient nouvelles; au fur et ä mesure de ses determinations il les avait décrites dans ses »Algologiske notiser«, mais sans les figurer. Aussi ai-je repris l'étude de toutes ces espéces-) de maniére å pouvoir donner ici un memoire d'ensemble ') Børgesen, F., The algal vegetation of the lagoons in the Danish West Indies. Biologiske Arbejder tilegnede Euo. Warming. København 1911. 2) Ce travail a été fait au Laboratoire de Cryptogamie du Museum d'His- toire naturelle de Paris (Professeur Mangin, membre de I'lnstitut). 10* 148 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. comprenant la description et la figuration de toutes les espéces recueillies. Les algues ont été récoltées par M. Boergesen å S*^ Jan, St. Thomas et S**^ Croix soit par draguage jusqu'å des pro fondeurs de 30 å 40 metres, soit å marée basse sur les cailloux, sur d'autres algues, et sur les récifs de polypiers oii les Mélobésiées abondent et vivent en compagnie des Bryozoaires. D'aprés la quantité considerable de matériaux recueillis il est peu probable que Ton trouve å l'avenir, dans ces iles, de nouvelles espéces, tout au moins d'espéces jouant un role important dans la flore. La flore des Mélobésiées des Antilles Danoises se compose de 20 espéces et représente une grande partie du nombre total des espéces recueillies jusqu'ici dans l'ensemble des iles des Antilles (environ 32 espéces). Voici la liste des espéces recueillies par M. Boergesen: Lithothamnium mesomorphum Fosl., var. ornatwn Fosl. et Howe: St. Jan. — sejunctum Fosl. : St. Croix, St. Thomas. — ruptile Fosl.: St. Jan, St. Croix, St. Thomas. — occidentale Fosl. : St. Jan, St. Thomas, St. Croix. Lithophyllum accretum Fosl. et Howe: St. Croix. — caribaeum Fosl. : St. Jan, St. Croix, St. Thomas. — erosum Fosl.: St. Thomas. — intermedium Fosl. : St. Jan. — daedaleum Fosl. et Howe: St. Croix. — strictum (Fosl.) Lemoine: St. Croix. — (?) absimile Fosl. et Howe: St. Jan, St. Croix. — (?)propin.quum (Fosl.) Lemoine : St. Jan, St. Croix, St. Thomas. — (Dermatolithon) prototypum Fosl.: St. Jan, St. Croix. Melohesia farinosa Lamx. : St. Jan, St. Croix, St. Thomas var. Solmsiana Falkb. : St. Jan, St. Croix, St. Thomas. — (Lithoporella) atlantica (Fosl.) Lemoine: St. Jan. — (Litholepis) affinis (Fosl.) Lemoine: St. Jan, St, Croix. — (Pliostroma) Chamaedoris Fosl. et Howe: St. Jan, St. Croix. Porolithon mamillare (Harv.) Lemoine, var. occidentalis Fosl.: St. Jan, St. Croix, St. Thomas. — Boergesenii (Fosl.) Lemoine : St. Croix. — pachydermum Fosl. : St. Jan. On voit dans le tableau precedent que le genre Lithothamnium est représente par 4 espéces, le genre Lithophyllum par 9, le genre Melobesia par 4 et le genre Porolithon par 3. H y a une pre- dominance tres nette d'espéces en croütes car deux espéces seulement sont des espéces ramifiées, et Tune d'elles, L. strictum est representee par une varieté naine, non ramifiée. Au point de vue de la structure, les espéces crustacées montrent pour la plupart un caractére interessant : c'est la F. Borgesen: Rhodophyceæ of the Danish W. Indies. 149 reduction de I'hypothalle. Je rappellerai que ce caractere se presents indifféremment chez certaines especes de chacun des genres Lithothamniiim, Lithophyllum, Porolithon. Alors qu'il parait rare dans les especes des regions européennes, ici on Tobserve dans 4 especes de Lithophyllum et 2 especes de Porolithon. J'ai cherché ä tracer aussi exactement que possible la reparti- tion et les affinités des especes des Antilles Danoises. II n'y a que trois especes qui soient connues ä la fois dans les Antilles Danoises et dans les mers européennes et africaines. Melohesia farinosa parait étre ubiquiste; les deux autres especes vivraient sur la cote atlantique africaine: Porolithon mamillare au Gap Vert, a St. Vincent et ä Algoa Bay d'apres Harvey; Porolithon Boergesenii å San Thome dans le Golfe de Guinée, oü d'aprés Fos lie, il serait représenté par sa varieté africana. Je n'apporte, pour ma part, aucune contribution ä ces faits. L'échantillon de la collection du Museum d'Histoire naturelle de Paris qui a servi ä créer la var. africana de P. Boergesenii est de si petite dimension que ce serait le détruire que de l'étudier; je ne sais si Foslie a eu en mains un échan- tillon plus important. En admettant que 3 especes des Antilles ont une repartition assez étendue, il reste 17 especes qui sont limitées å la region atlantique américaine: 12 especes vivent soit en Florid e, soit aux Bahamas en méme temps qu'aux Antilles Danoises; les autres especes, au nombre de 5, n'ont pas jusqu'ici été recueillies en dehors des Antilles ; enfm 3 especes de petite taille ne sont connues qu'aux Antilles Danoises. Ainsi il y a peu d'especes communes aux Antilles et å la region africano-européenne. Mais, d'autre part on ne peut pas ne pas étre f rappe d'une ressemblance extérieure tres grande entre certaines especes des Antilles et d'autres especes appartenant au méme genre et vivant dans la Méditerranée : ce fait est si net que, pour la plupart des especes, il est possible de mettre en regard de l'espéce des Antilles une espéce méditerranéenne d'aspect quelquefois si semblable qu'on pourrait les confondre : ce sont ces ressemblances que j'ai groupées dans le tableau suivant. Antilles : Méditerranée : Lithothamnium mesomorphum var. ornatum. Lithothamnium lichenoides. — sejunctum. — Lenormandi. — ruptile. — crispaium.. — occidentale. — [ruticulosum var. cla- vulata. 150 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Lithophyllum intermedium. — daedaleum. — (^) propinquum. — (D.) prototypum. Melohesia (Litholepis) af finis. Lithophyllum incrustans. — dentatum. — (F) Notar is ii. — (D.) papillosum. Melobesia (Litholepis) Sauvageaui. D'autres espéces montrent d 'autre part des analogies remar- quables avec les espéces de l'Océan Indien et du Pacifique : Antilles : Lithophyllum striatum. Melobesia (Lithoporella) atlantica. Porolithon pachydermum. — Antillarum.^) Indo- Pacifique: Lithophyllum frutescens. Melobesia (Lithoporella) melobesioides . Porolithon oncodes. — craspedium. Pour les espéces L. accretum, L. absimile, L. caribaeum, L. erosum, M. Chamaedoris, je ne connais pas d 'espéces af fines. Cette analogic d'aspect, souvent tres frappante, entre les espéces des Antilles Danoises et celles de la Méditerranée ou du Pacifique n'est qu'apparente : la structure offre souvent des carac- téres tres différents. Un cas typique est par exemple celui du Lithophyllum intermedium; par son aspect, et les caractéres de ses conceptacles, cette espéce ressemble å s'y méprendre å Litho- phyllum incrustans de la Méditerranée et des cotes européenne et africaine de l'Atlantique; bien plus, les deux espéces paraissent vivre dans les mémes conditions et forment sur les rochers des encroutements qui absitent une foule d'animaux ; or, le seul examen de la structure éloigne ces deux espéces l'une de l'autre ; L. incrustans montre un hypothalle épais forme de rangées con- centriques, tandis que dans L. intermedium 1 'hypothalle n'est représenté que par une unique rangée de cellules. Pour d'autres espéces les differences ne seront pas aussi profondes ; cependant les dimensions des cellules, l'aspect du tissu, les dimensions des conceptacles sont autant de caractéres autori- sant l'individualité des espéces des Antilles. Si j'ai insisté sur ces analogies, ce n'est done pas pour dis- cuter la valeur des espéces créées jusqu'ici, mais c'est plutot pour rechercher les relations et les affinités qui existent entre les espéces. Tableaux de determination des espéces des Antilles Danoises. Ainsi qu'il a été dit plus haut les espéces des Antilles Danoi- ses représentent une partie importante du nombre total des espéces connues jusqu'ici dans l'ensemble des Antilles. ') Cette espéce n'a pas été trouvée aux Antilles Danoises. F. Børgesen : Rhodophyceæ of the Danish W. Indies. lol Les especes des Antilles inconnues aux Antilles Danoises sont les suivantes: Lithophyllum acropetum Porto-Rico. — affine Porto-Rico. — congestum St. Barthelemy. — platyphyllum St. Martin. — (Dennatolithon) polyclonum. Lithothamnium aemulans Porto-Rico. Archaeolithothamniwn dimotum Porto-Rico. Porolithon improcerum Jamaique. — Antillarum Porto-Rico. Mastophora Lamourouxi Guadeloupe. Epilithon membranaceum Jamaique, Porto-Rico, Guadeloupe. D'autres especes ont été signalées aux Antilles par suite d'erreurs de determination et il ne doit pas en étre tenu compte; les échantillons appelés Lithophijllum incrustans (Collins 1901) doivent sans doute étre rapportés au Lithophyllum intermedium; Melobesia confervicola de la Guadeloupe (Maze et Schramm 1877) est le Melobesia farinosa d'apres Foslie ; le Melobesia callitham- nioides de la Guadeloupe également (Conquérant in herb. Bornet) est sans doute le M. farinosa var. Solmsiana ; d'autre part Foslie a range dans le Lithothamnium occidentale var. effusa des échan- tillons appelés tout d'abord par lui L. solutum var. eßusa (Foslie 1906, c): de méme les échantillons nommés primitivement PoroZi- thon oncodes (Weber et Foslie 1904) ont été ensuite avec raison distingués, sous le nom de Porolithon pachydermum, de ceux de rOcéan Pacifique ; de méme ceux nommés Lithothamnium Lenor- mandi sont devenus Lithothamnium sejunctum; enfm c'est certaine- ment par erreur qu'ont été signalés aux Antilles les especes: Lithothamnium polymorphum et L. amplexijrons (Maze et Schramm 1877); il semble également que le Melobesia Lejolisii (Collins 1901) n'atteigne pas la latitude des Antilles; certains échantillons de M. farinosa dépourvus d'hétérocystes sont difficiles å distinguer de M. Lejolisii. Quant au Lithophyllum (Derm.) pustulatum (Collins 1901) il serait possible que les échantillons dussent étre ranges plutot dans la var. Udoteae du Lith. (D.) prototypum ; les deux especes sont difficiles å separer lorsqu'il s'agit de petits échantillons sur algues. I. Conceptacles ä sporanges ayant leur toit percé d'un certain nombre de canaux. t Tissu différencié en hypothalle et périthalle; hypothalle forme de files horizontales de cellules Lithothamnium. 152 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. II. Conceptacles å sporanges ayant leur toit percé d'un seul pore. t Tissu différencié en hypothalle (souvent réduit å une seule rangée de cellules) et en périthalle. XX Tissu compose entiérement ou seulement en partie de rangées de cellules séparées les unes des autres par les cloisons tangentielles épaissies et plus ou moins soudées les unes aux autres Lithophyllum. XX Tissu généralement irrégulier souvent forme de cellules de formes et de dimensions variées; presence de grosses cellules soit isolées soit en groupes de 5 ä 8 Porolithon. t Tissu non différencié en hypothalle et périthalle; croutes tres minces formées d'une ou plusieurs rangées superposées . . . Melobesia. Genre liithothaniniuni. I. Espéces en croutes. Croüte tres adhérente, lobée et striée au bord, tres mince, sur pierres. Hypothalle: cellules rectangulaires 10 ä lb p.x 3 å 7//.: périthalle: cellules ovoides 5 å 7 // x 3 å 7 //.. Conceptacles å sporanges ItO å 260,«; 40 canaux dans le toit; conceptacles ä cystocarpes 200 ä 300 fj. L. sejunctum Fosl. Croüte peu adhérente formant souvent des lamelles libres orbicu- laires, minces et fragiles, brillantes. Tissu lache; hypothalle: cellu- les rectangulaires: 10 å 14 jusqu'å 25/^x4 å 7//.; périthalle: cellules arrondies de 10 å 12//. x 7 å 10 /j. ä la base, 5 å 8//x5 ä 7 fj. au sommet. — Sterile L. mesomorphum Fosl. var. ornntum Fosl. et Howe. Croutes peu adhérentes, minces, irréguliéres, d'aspect variable. Ti^su lache; hypothalle: files entremélées, cellules reet. -ovoides 20 ä30/y. X 7 å 10//; périthalle: cellules ovoides de 10 ä 15 //x 7 å 10 fj.. Conceptacles ä sporanges 500 ä 700// L. ruptile Fosl. II. Espéce en branches. Tissu forme de files laches distinctes ; cellules rectangulaires-ovoides 10 å 30 // X 6 å 10 //. Souvent sterile L. occidentale Fosl. Genre Lithophyllum. I. Espéces en croutes. t Hypothalle forme d'une seule rangée de cellules. X Croutes tres minces. Surface rugueuse ; hypothalle ; cellules 5 å 7 /i x 5 å 12 /y. ; péri- thalle tissu compact, cellules rectangulaires 3 å 6 // x 3 å 8 //.. Conceptacles en petits granules convexes de 80 ä 120/7.; ä maturité petites cavités L. caribaeum Fosl. Cellules en files distinctes å la base, plus serrées ä la partie supérieure, b kl /j.x1 fi. Conceptacles de forme ovale ; partie centrale du 'toit déprimée entouré par un rebord ovale L. erosum Fosl. X Croutes épaisses mamelonnées ou pourvues d'excroissances. Périthalle primaire: files cellulaires distinctes; cellules rec- tangulaires de 7 å 20 /! X 5 ä 8 p., disposées au méme niveau. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 153 Périthalle secondaire: files serrées; cellules de 10 å 22/^x5 å 12//., en rangées. Ecorce: cellules 5/txlO/a. Gonceptacles convexes de 250 å 380 fj. ; sporanges 60 /j x 30 ä 55 //.. Gon- ceptacles ä cystocarpes convexes-coniques 200 ä 350 // L. dædaleum Fosl. et Howe. Hypothalle: cellules 10 ä 12//. x4/j!. Perithalle: cellules de 8 å 15 p. jusqu'ä 20 /j.xb äl /j., en rangées ä la base, en files distinctes ä la partie supérieure. Gonceptacles 150 ä 300// de diametre formant de petites depressions ä la surface du thalle L. intermedium Fosl. t Hypothalle forme de rangées concentriques. Hypothalle: cellules 7 ä 12/^x5 ä 10/^. Périthalle: cellules de 5 å 12 /y. X 5 å 15/^, au méme niveau souvent en rangées; parois des cellules tres épaisses. Gonceptacles 300 ä 400 ß, de forme ovale, avec la partie centrale du toit déprimée L. accretum Fosl. et Howe. t Hypothalle forme de files cellulaires non disposées en rangées (structure aberrante dans le genre Lithophyllum). Croute adhérente, lobée, ä surface irréguliére. Hypothalle épais; cellules de 10 ä 12/^-. x6 ä dp., plus rare- ment jusqu'ä 18 et 22//.. Périthalle tres épais, cellules de 3 ä 7 /Jt X 2 å 3 // en files distinctes ; périthalle traverse par des lignes colorées. Gonceptacles tres serrés, convexes, de 100 ä 160 fj. de diametre L. absimile Fosl. et Howe. Croüte peu adhérente, mince, lobée, quelquefois pourvue de lamelles. Hypothalle files serrées rigides, cellules rectangulaires 15 å 35 //x 7 ä 12//; périthalle: cellules rectang. en rangées: 7 ä 11 //X 5 ä 12//. Gonceptacles tres gros, coniques, de 300 å 1200//, quelquefois prolonges par des épines. Sporanges 90 å 160 // X 40 å 60 // L. propinquum Fosl. II. Espéce en branche. Groute mince, lobée surmontée de nombreuses petites branches cyhndriques non ramifiées de 4 mm de hauteur et 1 mm de diametre. Tissu forme de rangées ; cellules rectangulaires 12 å 20 // X 7 å 16// L. strictum Fosl. var. nana Fo.sl. et Howe. Sous-Genre Dermatolithon. Périthalle forme entiérement de hautes cellules rectangulaires pourvues de pores, disposées en rangées. Hypothalle forme de cellules obliques, contournées, de grande taille. Groutes tres adhérentes recouvertes d'un grand nombre de tres petites lamelles. Tissu compose de 6 å 12 rangées qui se séparent les unes des autres; cellules de 7 å 35//xl0 ä 15//; chaque rangée est recouverte d'une rangée de petites cellules corticales de 3 å 5// ; hypothalle peu difTérencié ; cellu- les de 40 ä 80 //.. Gonceptacles å sporanges hémisphériques de 350 ä 600//; sporanges: 60 ä 80//X35 å 50//. C. å cysto- carpes coniques, 450 å 550/« L. (D.) prototypum Fosl. 154 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Genre Melobesia. Croutes sur algues, d'abord circulaires formant ensuite des croutes plus étendues, tres minces. Thalle constitué en cOupe par 3 ran- gées de cellules. Vu de dessus tissu caractérisé par des hétéro- cystes. Conceptacles de 60 å 250//. M. farinosa Lmx. Sous-Genre Litholepis. Croutes saxicoles, tres fines, semblables å une poussiere puis formant des thailes circulaires ; thalle forme d'une seule rangée de cellules. Croutes poussant les unes au-dessus des autres. Conceptacles petits. Cellules de 14 ä 22/iX9 ä 18 a. Conceptacles de 60 ä 260, a. M. (L.) affinis (Fosl.) Lem. Sous-Genre Lithoporella. Croutes minces, sur coraux, poussant les unes au-dessus des autres. Thalle forme d'une ou deux rangées de cellules. Conceptacles tres gros, coniques. Cellules de 18 å 32 ß x 10 å 25 //. quelquefois atteignant 60 /j. X 40 /i. Conceptacles ä sporanges de 500 å 800 ,u M. (L.) atlantica (Fosl.) Lem. Sous-Genre Pliostroma. Croutes tres minces sur algues et pierres, constituées par plusieurs rangées de cellules, sauf ä la marge qui n'est formée que d'une seule rangée. Conceptacles petits, convexes. Cellules de 7 ä 13 X 8 å 10 //. Conceptacles de 150 å 200 //.. M. (P.) Chamædoris Fosl. et Howe. Genre Porolithon. Hypothalle iormé d'une rangée de cellules. Croüte épaisse. Hypothalle: cellules 20 ä 25,«x8/j'.. Péri- thalle: tissu irrégulier, cellules de 7 ä 18 //. x 8 å 12/<; grosses cellules isolées de 20 å 25/aXl8 ä 20/7.. Conceptacles å sporanges : 300 å 400 p. P. Boergeseni Fosl. Croüte mince, lobée, peu adhérente, pourvue de nombreuses épines et de lamelles. Cellules de l'hypothalle peu différenciées ; périthalle cellules 10 å 20/7. x 7 å 15//; parois des cellules minces. Conceptacles tres gros coniques de 1 mm, 4 P. mamillare Harv. Hypothalle forme de files horizontales de cellules. Croüte adhérente sur coraux. Hypothalle forme de quelques files ; cellules de 8 å 17 /7. x 4 å 10 rj.. Périthalle tissu compact, cellules 4 å 8 //. x 7 å 12 tj.. Grosses cellules en groupe de 8, de 17 å 20 /7. X 8 å 15 p.. Conceptacles å sporanges convexes 150 ä 250 fj. de diametre ; sporanges de 60 å 70 ß x 30 ä 40 ß. Cone, ä cystocarpes convexes de 200 å 300//. P. pachydermum Fosl. I F. Børgesen: Rhodophyceæ of the Danish W. Indies. 155 Lithothamnium Phil. 1. Lithothamnium mesomorphum Foslie. 1901. Lithothamnium mesomorphum Foslie, New. Melob., p. 5. 1906. Lith. mesomorphum ornatum Foslie et Howe, New. Amer. Corall. alg., p. 129, pi. 80, fig. 2, pi. 90, fig. 2. Lithothamnium mesomorphum est représenté dans la collection de M. BoERGESEN par quelques échantillons appartenant å la YRnéié ornatum; ils forment de petites lamelles fragiles, deforme d'abord circulaire puis ensuite orbiculaire, fixées seulement par un point de la face inférieure ou par une extrémité; lamarge est blanche et légérement épaissie. Cette espéce peut également se presenter sous I'aspect de croütes qui montrent, comme les la- melles, une surface brillante; ces croütes se détachent facilement des coraux sur lesquels elles sont fixées et elles ont une tendance marquee å la formation pa et lå de petites lamelles orbiculaires dressées. Par son aspect brillant, sa surface striée et ses gros concep- tacles L. mesomorphum rappelle beaucoup l'espéce atlantique et mediterranéenne L. lichenoides ; la var. ornatum a aussi une cer- taine ressemblance avec L. expansum de la Méditerranée, en particulier avec sa var. tenuis. L. mesomorphum var. ornatum est généralement sterile ; dans la forme type les conceptacles å sporanges ont de 350 å 600 /< de diametre, de forme peu défmie ; leur toit est percé de nombreux canaux; les sporanges mcsurent 100 å 140 fi de longueur et 60 /^ de largeur. En coupe L. mesomorphum montre une structure tres lache avec de larges interstices entre les files de cellules; l'hypothalle est forme de cellules rectangulaires ; de 10 å 14 /i de longueur et 4 å 1 11 de largeur, et méme de 20 å 25 /i x 4 å 7 /i ; il est peu développé, forme seulement de quelques fdes. Les cellules du périthalle qui lui font suite sont arrondies, elles mesurent 10 å 12fj.xl å 10/^ pres de l'hypothalle et vont en diminuant de taille vers la partie supérieure de la croute oii elles ne mesurent que 5å8/ix5å7/^. L'épaisseur des croütes est de 300 å 500 /i. St. Jan: Entre Cruz Bay et Great St. James, No. 2143, profondeur 15 brasses; au large d'Annaberg, No. 1989, prof. 15 brasses 'la. Repartition géographique: L. mesomorphum a été signalé aux Iles Bermudes (Herbier Bornet, échantillons récoltés par le General Lefroy en 1873 et par M. Farlow en 1881); Howe l'a recueiUie aux Iles Bahamas. Il n'avait pas encore été signalé aux Antilles ; il n'est d'ailleurs représenté que par quelques échantillons recueiUis ä une certaine profondeur ; il parait 156 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. done rare aux Antilles Danoises. C'est une espéce å rechercher, å cause de sa fragilité, dans les endroits abrités et les anfractuosités des rochers et des récifs. 2. Lithothamuium sejiinctura Foslie, 1906. Lithothamnium sejunctum Foslie, Alg. Not. II, p. 13. L. sejunctum forme, sur les pierres, de petites croutes adhé- rentes tres minces, lobées au bord et liserées de blanc sur les échantillons sees; l'aspect est assez voisin de celui de L. Lenor- mandi commun sur les cotes européennes de l'Atlantique, en particulier de sa varieté suhlævis. Les conceptacles å sporanges mesurent 160 å 260 /i de dia- metre; leur toit est percé de 40 canaux, Les conceptacles å cystocarpes mesurent 200 å 300/^. En coupe verticale on observe la presence de l'hypothalle et du périthalle. L'hypothalle est forme de quelques files de cellules; les cellules sont rectangulaires, légérement ovoides, de 10 å 15 ^u de longueur et 3 å 1 [j. de lar- geur. Les cellules du périthalle sont ovoides, de 5 å 7 // de ^ /l longueur et 3 ä 7// de largeur. „..-„„ X- 1 j, >x L'analogie d'aspect extérieur Flg. 150. Coupe verticale d une croüte *? ^ de Lithothamnium sejunctum. entre L. sejunctum et L. Lenor- mandi n'est pas accompagnée d'une analogie complete dans la structure; en effet les cellules de Thypothalle de L. Lenormandi mesurent 15 å 22// x 3 å 4/7. ; elles sont rectangulaires å angles vifs; les cellules du périthalle sont rectangulaires-ovoides et mesurent 6 å 9« x 4 å 5//; les conceptacles å sporanges et å cystocarpes sont un peu plus grands et mesurent 200 ä 400 /7; enfin le toit du conceptacle est dissous dans sa partie centrale et il reste une bordure annulaire carac- téristique. St. Croix: Christiansted. St. Thomas cote Nord. Repartition géographique. Cette petite espéce n'a pas jusqu'ici été recueillie en d'autres localités. 3, Lithothamnium ruptile Foslie. 1905. Lithothamnium syntrophicum Fos\. f. ruptilis Fosl. ; Foslie, Botan. Saml. (1904) 1905, p. 18. 1907. Lithothamnium ruptile Foslie, Alg. Not. Ill, p. 5. Lithothamnium ruptile se présente sous l'aspect de croütes minces, irréguliéres, souvent contournées, 'poussant les unes au- F. Børgesen: Rhodophyceæ of the Danish W. Indies. 157 dessus des antres et formant ainsi une croiite complexe qui se libere de son substratum; la croiite peut s'enrouler sur elle-méme en certains points de maniére å simuler des sortes de petites coupes évasées ou des sortes de branches creuses. L'aspect est en somme assez variable, mais les croütes se distinguent de la plupart des autres espéces des Antilles parce qu'elles ne sont pas adhérentes au substratum. Cette espéce rappelle beaucoup, Lithothamnium crispatum de la Méditerranée et L. syntrophiciim. Les conceptacles å sporanges sont de grande taille et mesurent 500 å 700// de diametre. En coupe on observe que l'hypothalle est forme d'un certain nombre de files laches et entremélées ; les cellules sont rectangulaires-ovoides et mesurent 20 å 30/2 de longueur et 7 å 10/^ de largeur. Lorsqu'il y a formation d'une excroissance l'hypothalle y contribue en formant des files verticales dont les cellules sont rectangulaires et mesurent 25 å 30/^ X 9 å 14//; l'hypothalle est continue par le périthalle dont les cellules ovoides et gonflées en forme de ballon mesurent 10 å 15/^ de longueur et 7 å 10// de largeur. pig, ^g^ Croute de Lithothamnium St. Thomas: Thatch Cay, ruptile (grandeur naturelle). No. 1967 ; St, J an : Au large de Cruz Bay, No. 1826, 2142. St. Croix: White Bay, No. 1590. Repartition géographique. Cette espéce a été signalée å St. Do- mingue; peut-étre est-ce la méme espéce qui aurait été signalée aux Ber- mudes sous le nom de L. syntrophicum (Foslie 1901). 4. Lithothamnium occijleutale Foslie. 1906. Lithothamnium fruticulosum (Kütz.) Fosl., var. occidentale Foslie, Alg. Not., II, p. 12 1908. Lithothamnium occidentale Foslie, Nye Kalkalg., p. 3 (f. effusa Fosl.). Cette espéce constitue de petits massifs formes de branches ramifiées souvent coalescentes ; l'aspect en est souvent informe et peu elegant; il est probable que eet aspect résulte de conditions de vie nuisibles å l'espéce, car les branches sont quelquefois creuses en leur partie centrale et l'espéce est souvent sterile. Des échan- tillons mieux développés, formes de branches fines et divergentes ont été groupés par M. Foslie dans la varieté effusa. 158 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. En coupe le tissu est compose de files cellulaires laches, séparées les unes des autres; les cellules sont rectangulaires, légére- Fig. 152. Thailes de Lithothamnium occidentale (grandeur naturelle). -^^ ment gonflées, elles mesurent 10 å 20/^, jusqu'å 32 {i de longueur et Q klOfj. de largeur; elles sont en somme de taille tres variable; les cloisons ne se colorent pas fortement par les réactifs. L'espéce a montre jusqu'ici des conceptacles jeunes ou mal développés ; cependant dans une coupe j'ai observe une tétraspore qui mesurait 180 // de longueur 30 fi et lö/j. de largeur. S t. J a n : Au large d'Annaberg No. 1989, profondeur 15 brasses ; au large d'America Hill, No. 2072, 2003; au large de Cruz Bay No. 1826, 1917, 1727, 2221. Entre St. Jan et St. Thomas, (Dr. Th. Mortensen); entre St. Jan et Thatch Island No. 1995. St. Tho- mas: Ouest de Water Island, No. 1178, profondeur 20 brasses. St. Croix: White Bay, No. 1.590. Repartition géographique. Cette espéce a été signalée ä St. Do- mingue. Aux Antilles Danoises il faut noter son abondance ä St. Jan et sa faible abondance a St. Croix. Fig. 153. Files cellulaires de Litho- thamnium occidentale. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 159 Lithophyllum Phil. 1. Lithophyllum accretum (Fosl. et Howe) Lem. 1906. Goniolithon accretum Fosl. et Howe, New Amer. Corall. Alg., p. 131, pi. 85, fig. 2, pi. 91. Cette espece se présente sous I'aspect de croutes circulaires qui se réunissent en formant des croutes d'une certaine étendue, adhérant tres fermement au substratum; I'epaisseur est générale- ment de 80 ä 350 ^ ; elle peut atteindre 1 mm. 3 ; elles sont lobées au bord, et striées ; la marge est un peu plus épaisse; ä la limite de deux thalles, il y a formation d'un rebord. Cette espéce recouvre L. caribaeum et est å son tour recouverte par L. inter- medium et L. propinquum. La surface est couverte de conceptacles jusqu'å la marge; les conceptacles å sporanges sont convexes, peu saillants ; la partie centrale du toit s'affaisse légérement et est entouré par un rebord ; les conceptacles å cystocarpes sont légérement coniques et å maturité laissent å leur place un trou ; le diametre des conceptacles est de 300 å 400;/. En coupe L. accretum montre un hypothalle compose de cellules de 7 å 12 « x 5 å 10//, disposées å peu pres réguliére- ment en rangées concentriques ; les cloisons séparant les rangées sont plus OU moins épaissies, en certains points elles atteignent bfjL. Dans les croiites minces, l'hypothalle occupe presque toute l'épaisseur de la croute ; dans des croutes plus épaisses, on observe le périthalle forme de cellules tres larges de 5 å 12 // de longueur et 5 å lo fj. de largeur, les membranes des cellules sont tres épaisses ; les cellules sont disposées au méme niveau et en certains points forment des rangées. En dehors des échantillons de Boergesen, j'ai étudié ceux de HowE provenant aes Bahamas; on remarquera que ma des- cription basée sur l'étude de ces échantillons différe de celle donnée par Foslie et Howe: ces auteurs ont donné pour les cellules de Thypothalle les dimensions 14 å 27 « x 8 å 14/^, et pour celles du périthalle 4 å 9/i. D'ailleurs la figure qu'ils ont donnée pi. 91 ne ressemble pas å la coupe que j'ai obtenue en étudiant l'échantillon de Howe des Bahamas; cette figure rap- pellerait plutot la structure de Lithophyllum absimile. St. Croix: Sur caillou dans l'eaii peu profonde. Repartition géographique. L. accretum a été signalé en Floride: Sands Key; aux Bahamas ; aux Antilles il n'avait encore été signalé qu'avec doute ä Porto-Rico. 160 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 2. Lithophyllum (?) caribaeum Fosl. 1906. Lithophyllum decipiens Fosl., f. caribaea Fosl., Alg. Not. II, p. 18. 1907. — caribaeum Fosl., Alg. Not. III, p. 22. 1909. — — Fosl., Alg. Not. VI, p. 11. Cette espéce forme, sur les pierres, des croutes tres minces dont la surface, sauf sur les pierres schisteuses, est légérement rugueuse ; au debut les croutes se développent en grand nombre et ne recouvrent pas complétement le substratum; puis elles se réunissent et forment des croutes étendues qui sont tres souvent cachées en partie par des espéces dont les thalles sont plus épais comme L. propingimm et L. intermedium (fig. 159) et L. accretum. Les conceptacles forment de petits granules souvent si nombreux qu'ils couvrent toute la surface ; leur diametre est de 80 ä 120//; ä maturité ils laissent å leur place de petites cavités. La structure de cette espéce å pour caractére principal la reduction de Fhypothalle forme d'une seule rangée de cellules rectangulaires de 4 å 7 a de hauteur et 5 å 12// de largeur. Le périthalle forme un' tissu tres compact; les files cellulaires sont tres serrées; Fig. 154. Coupe verticals du thalle de j^g cellules sont tres petites Lithophyllum caribaeum. , , . ■, n ^ n j rectangulaires de o a b/z de longueur et 3 å 8/^ de largeur. Dans les échantillons étudiés le tissu ne montrait pas une disposition en rangées tres nette ; aussi cette espéce doit-elle étre placée parmi les espéces aberrantes du genre. St. Croix: Port de Christiansted, dans l'eau peu profonde. Estate Northside, sur les roches exposées. No. 1468. St. Jan: Cruz Bay, No. 2196; Great Cruz Bay, No. 1782, 1783. St. Thomas: Pres de Water Island, profondeur 15 brasses. No. 1161. Repartition géographique. L. caribaeum parait étre une des espéces caractéristiques des Antilles et des Bahamas. Aux Antilles, en dehors des locaUtés indiquées, elle a été recueillie å Porto-Rico par Howe. 3. Lithophyllum erosiim Fosl. 1906. Lithophyllum erosum Foslie, Alg. Not. II, 1906, p. 20. L. erosum forme sur les cailloux des croutes tres minces (en coupe 40// environ) qui suivent la forme et les aspérités du substratum; le contour est tres découpé. Les conceptacles sont petits, peu proéminents, souvent de forme ovale; puis le toit est déprimé dans la partie centrale et F. Borgesen: Rhodophyceæ of the Danish W. Indies. 161 enfin Faspect est celui d'une petite cavité ovale entourée par un rebord ; en dernier lieu le rebord lui-meme a disparu. En coupe I'un d'eux mesurait SO/j. de large et 40 /^ de haut. Le tissu est compose de petites cellules rectangulaires de 5 å 1 fi et 10// de longueur et 7// de largeur, fortement colorées par les réactifs, disposées en files distinctes å la base et plus serrées å la partie supérieure. L'hypothalle est représenté par la rangée basilaire de cellules. Je n'ai pas observe de rangées dans le tissu qui par conse- quent, de méme que L. caribaeiim, doit étre place apart dans le genre L?/ÄoöÄv//«wz. ^. ^^^ „.^ i, . t-, ^ ^ » ' ^ . Fig. 155. Thalles de Z,i«Äo- St. Thomas: Pres de la cote, dans Ma- phyllum erosum. gens Bay. Repartition géographique. L. erosum n'a pas encore été signalé en d'autres localités. 4. Lithophyllum intermedium Fosl. 1901. Goniolithon? (Cladolithon) intermedium FosUe, New Melob., p. 15. 1906. Lithophyllum intermedium Foslie, AJg. Not. II, p. 23. L. intermedium forme å l'état jeune, de petits thailes de forme circulaire, lobés ou crénelés aux bords, qui recouvrent d'autres croiites plus minces comme L. caribaeiim et L. propinquum, ainsi qu'on le voit fig. 161. A un stade plus développé, le thalle s'agrandit, la sur- face devient mamelonnée (Fig. 156) et lorsque plusieurs thalles, développés sur le méme substratum viennent å se ren- contrer, leur bord se reléve en formant une créte dressée, ondulée. L'aspect de l'algue, soit jeune, soit plus ågée lorsque sa surface est mame- lonnée, rappelle celui de Lithophyllum incriistans et de Pseiidolithophyllum dis- coideum; ces trois espéces si différentes de structure ont un aspect presque semblable ; toutes trois vivent dans la zone littorale, sur les rochers accessibles å marée basse. Les conceptacles tres nombreux forment une multitude de petits points, puis de petits trous, dont la surface du thalle est véri- tablement piquetée ; leur diametre est de 150 å 300«. En coupe on observe que le tissu est forme par le périthalle : l'hypothalle forme seulement la rangée basilaire de cellules qui Fig. 156. Croüte de Litho- phyllum intermedium ( mar- quee d'une croix). Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 11 162 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. mesurent 10 å 12;^ de hauteur et iju de largeur. Les cellules du périthalle mesurent 8 ä 15/>« de longueur et peuvent atteindre 20 /u ; leur largeur est 5 å 7 /^ ; les cloisons tangentielles sont épaissies et la disposition en rangées est généralement assez nette, surtout å la partie inférieure du thalle. . 5j„ s t. J a n : Cruz Bay, No. 2196 ; Great ^ Cruz Bay pres de la cote No. 1783, 1782. Repartition géograpliique. L. intermedium a été signalé aux Bermudes Fig. 157. Coupe verticale de la ( Wadsworth in herb. Farlow) ; en Floride croute de Lithophyllum inter- (Waerdeman herb. Farlow, in herb. medium. Ä, hypothalle. Bornet); aux Antilles : Barbade (Vickers in herb. Bornet], Lassen (Herb. Børge- sen), Jamaique (Collins, Howe) et avec plus de doute å Porto-Rico, (Howe, No. 2346, voir Foslie 1906, p. 23). 5. Lithophyllum daedaleum Fosl. et Howe. 1906. Lithophyllum daedaleum Fosl. et Howe. New arner. Corall. alg., p. 133, pi. 83 et 84, pi. 93 (microphotographie) ; var. pseudodentala Fosl. et Howe, pi. 85, fig. 1. 1909. Lithophyllum daedaleum Fosl. et Howe; Foslie, Alg. Not. VI, p. 37. Lorsque cette espéce atteint son complet développement, elle forme, sur les cailloux, des croutes de O "^'",5 å 2 mm d'épaisseur, qui donnent naissance ä des mamelons irréguliers ou å des sortes de courtes branches, plusieurs fois ramifiées et souvent anastomo- sées ; ces branches ont environ 2 mm d'épaisseur ; elles sont tres épaissies å leur sommet, souvent tronquées ou méme déprimées en leur centre ; lorsque ces branches sont irréguliérement dilatées, elles apparaissent comme des replis de 3 å 15 mm d'épaisseur. Dans la var. pseudodentala, la plupart des branches sont tres comprimées et sont élargies en forme d'éventail å leur partie supérieure ; elles peuvent ainsi atteindre une largeur de 2 cm. Les échantillons de M. Boergesen se présentent simplement sous l'aspect de mamelons irréguliers prolonges par de fines épines; ils forment des thailes de 2 å 3 cm de hauteur. La coupe étudiée traversait une portion de la croute de 1 mm 600 /i d'épaisseur. A la partie inférieure du thalle on observe des files cellulaires tres distinctement séparées les unes des autres ; les cellules sont rectangulaires et mesurent 7 å 20 /^ de longueur et 5 å 8// de largeur; les dimensions moyennes sont 12 å 17^« X 7 // ; elles sont en general situées au méme niveau dans les F. Børgesen: Rhodophyceæ of the Danish W. Indies. 163 différentes files ; les cloisons se colorent fortement par les réactifs colorants. Vers la partie supérieure de la coupe, le tissu prend un aspect plus compact : les files sont plus serrées et les cellules se dispo- sent dans leur ensemble en rangées horizontales ; les cellules pour- vues chacune d'un pore, mesurent 10 ä 22// x 5 ä 12//, Enfin å ce second tissu ou périthalle secondaire, fait suite une écorce formée de tres petites cellules rectangulaires tres serrées, plus larges que hautes et disposées en rangées; leur dimension moyenne est 5// x 10//. Suivant l'épaisseur de la croiite étudiée, elle peut étre constituée soit seulement par le premier tissu (périthalle primaire) soit par les deux tissus super- poses (périthalles primaire et secondaire). L'écorce peut se former ä la suite du périthalle primaire et se trouver ainsi intercalée au milieu de l'épaisseur du tissu ; les cellules de l'écorce se recon- naissent toujours å leur aspect et å leur faible coloration, par les réactifs, par rapport aux autres cellules, L'hypothalle parait étre représenté par une unique rangée de cellules in- colores å la base du thalle, Les conceptacles å sporanges sont convexes, peu proéminents, de 250 å 3S0 fi de diametre d'aprés les auteurs; les sporanges mesurent 60 /j. de longueur et 30 ä 35 /^ de largeur. Les conceptacles å cystocarpes sont trant' la superposition des ., ^ , . , dmerents tissus. convexes, Jegerement comques, et mesu- rent 200 å 350/^ de diametre. Les conceptacles å anthéridies sont encore inconnus. St. Croix: Le port de Christiansted. Repartition géographique. Cette espéce a été signalée aux An- tilles: Porto-Rico: Salinas Bay pres Guanica ; Ile Culebra; Santurce; San Juan (FosLiE et Howe 1906). Elle vivrait probablement aussi au Venezuela: Margaritaoen, au Brésil (localité inconnue) et ä I'Ile de la Trinidad (herb, du British Museum, échantillon nommé précédemment L. pallescens; voir FosLiE, 1909, p. 37,. 11* Fig. 158. Coupe verticale de Lithophyllum daedaleum mon- 164 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 6. Lithopliyllum strictum (Fosl.) Lem. var. nana Fosl. et Howe. 1901. Goniolithon? (Cladolithon) strictum Foslie, New Melob., p. 14. 1906. Goniolithon strictum Foslie; Foslie et Howe, New Arner. Corall. alg., p. 131, pi. 82, fig. 1. 1907. Gonial, strictum Foslie, Alg. Not. III, p. 16 (var. fastigiata Fosl.). Lithophylliim strictum est une tres jolie espéce formant un massif de branches tres ramifiées ; l'aspect varie suivant le nombre de ramifications et le diametre des branches ; les branches sont dressées ou un peu courbées et s'amincissent légérement vers la partie supérieure ; les ramifications sont souvent espacées et les branches prennent naissance fréquemment presque å angle droit sur les branches principales ; les derniéres ramifications sont géné- ralement bifurquées au sommet et les extrémités sont arrondies. L'espéce ne parait pas étre representee aux Antilles Danoi- ses par des échantillons types ; M. BoERGESEN y a seulement trouvé la varieté nana qui en différe profondément d'aspect. Dans cette varieté l'algue déve- loppe sur des cailloux une croute å contours largement lobés; d'autres lobes peuvent se former pa et lå sur la surface de la croute ; cette croute ne s'épaissit pas et donne rapidement naissance å de petites branches cylindri- ques non ramifiées, de 1 mm environ de diametre qui se dressent verticalement sur toute la surface de la croute, sans dépasser 4 mm de hauteur. En coupe les échantillons de la var. nana montrent un tissu forme de rangées de cellules rectangulaires tres larges, mesurant 12 å 20 /i de longueur et 7 å 10// et méme 15 et 17 /^ de largeur. Les cellules de la var. nana sont plus petites que celles des échantillons bien développés de L. strictum type ; ceux-ci, sur un échantillon de Floride m'ont montre des cellules de 16 å 33 fx X 12 å 13 fjt, et Foslie a méme observe en coupe longitudinale les dimensions suivantes 25 å 55// x 15 ä 25^«. St. Croix: Longford; Long Reef, No. 1272, 1274; Christiansted. Fig. 159. Aspect extérieur de Litho- phyllum strictum var. nana. F. Børgesen : Rhodophyceæ of the Danish W. Indies. 165 Repartition géographique. L. strictum a été signalé aux An- tilles; ä la Jama'ique, ä Porto-Rico; aux Bahamas d'ou Howe en a rap- porté de magnifiques échantillons ; en Floride (Agassiz, herb. Farlow), Soldiers Key, Key West (Howe, Farlow in herb. Bornet). 7. Lithophyllum (?) absimile Fosl. et Howe. 1907. LithophiiUuni absimile Fosl. et Howe; Foslie, Alg. Not., IV, p. 27. I- S.Oft Fig. 160. Partie du tissu péri- phérique (périthalle) des branches de Lithophyllum strictum. Je rapporte å cette espéce des croutes de St. Jan dont l'aspect rappelle ä premiere vue celui de Lithophyllum intermedium; lacroiite est épaisse d'environ 1 mm, lobée et striée aux bords. Les conceptacles sont tres petits, tres serrés et convexes ; ils ne paraissent jamais étre enfoncés dans le thalle ce qui les différencie de ceux de Lit. intermedium ; les conceptacles observes en grand nombre mesuraient 100 å 150/^ et méme 200/^ de diametre; ces dimensions ne sont pas éloignées de celles indi- quées par Foslie et Howe (120 å 160 n de diametre). Les spor- anges n'ont pas encore été observes. En coupe on observe un hypothalle bien développé; les cellules sont courtes, elles mesurent 10 å 12^^^, plus rarement 18 et 22 n de longueur et 6 å 9 « de largeur. Le périthalle, tres épais, est forme de tres petites cellules de 3 å 1 ix de longueur et 2 å ^n de largeur, en files séparées les unes des autres. Le péri- thalle est traverse par des lignes qui se colorent par les réactifs colorants, et qui sont distantes les unes des autres de 10 å 20^^ environ. Les cellules périthalliennes rappellent celles de L. caribaeum; cette derniére espéce forme une croiite beaucoup plus mince et l'hypothalle est réduit. Ces deux espéces ne montrent pas la disposition en rangées caractéristique du genre Lithophyllum et doivent étre considérées comme des espéces d 'attribution incertaine. Les croutes de la collection de M. Boergesen ont été trouvées ä St. Jan: Cruz Bay, No. 2196, No. 1783, sur une pierre en compagnie de L. carlbaeum, L. proplnquum, L. intermedium, St. Croix: Christiansted. C'est sans doute la méme espéce qui forme une croüte tres abimée provenant de St. Croix; la structure y est altérée. Repartition géographique. L'espéce n'a etc jusqu'ici signalée qu'ä la Jamaique. 166 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 8, Lithophyllum (?) propinqiiimi (Fosl.). 1900. Goniolithon (CladoUthon) Notarisii Duf., f. propinqua Fosl., New or crit. calc. alg. (1899), p. 21. 1906. Gon. Notarisii Duf., f. propinqua Fosl.; Foslie, Alg. Not., II, p. 15. 1907. Gon. solubile Fosl. et Howe; Foslie, Alg. Not., IV, p. 21. 1908. Gon. propinquum Fosl ; Foslie, Nye Kalkalger, p. 4 (f. imbicilla Fosl., f. solubilis Fosl. et Howe). L. propinquum forme sur les pierres des croiites å contour lobe, pourvues de gros conceptacles coniques; ces croiites sont bien visibles fig. 161, oü elles recouvrent L. caribaeum; elles sont elles-mémes recouvertes å droite de la figure par L. intermedium. Steriles, les croutes ont souvent une sur- face unie, sauf dans la var. imbicilla qui montre de petites lamelles, et dans la var. solubilis qui forme sur coraux des croutes ä sur- face inegale. Les croutes se détachent assez facilement du substratum lors- qu'elles sont agées. Les conceptacles souvent développés en grand nombre et tres serrés, sont tres larges å leur base et de forme generale conique ; le diametre est de 300 tj. å 1 mm. pour les conceptacles å sporanges, de 500 ä 1200 /i pour les conceptacles å cystocarpes et de 300/^ pour les conceptacles å anthéridies. Les conceptacles sont prolonges par une épine caduque courte dans les conceptacles å cystocarpes et plus allongée dans ceux å sporanges. Les sporanges mesurent 90 å 160// de longueur et 40 å 60// de largeur; les carpospores observées dans une de mes coupes mesuraient 70 å 80/^ x 20 å 30//, En coupe le tissu est forme d'un hypothalle et d'un périthalle. L'hypothalle est forme de files serrées, rigides ; les cellules, rectangulaires, mesurent dans les échantillons étudiés 15 å 35 // de Fig. 161. Croutes de Lithophyllum propinquum pourvues de conceptacles å cystocarpes. Au centre les croutes blanches marquees d'un v appartiennent au L. caribaeum ; å droite un thalle de L. inter- medium marqué d'une double croix. — 30^ F. Børgesen : Rhodophyceæ of the Danish W. Indies. 167 longueur et 7 ä 12// de largeur ; cependant, d'aprés Foslie, elles atteindraient bb p. de longueur. Le périthalle est forme de cellules rectangulaires disposées å la fois en files et en rangées ; le tissu présente un aspect compact, les cellules sont tres serrées, elles mesurent 7 å 11 ix de hauteur, jusqu'å 25 ^^ et 5 ä 12/z de largeur, L. propinguum rappelle Pespéce méditerranéenne L. Notarisii et aussi L. pacificum du Japen. St. Jan: Cruz Bay, No. 2196; Fig. 162. Tissu périthallien de Litho- Great Cruz Bay, No. 1782 ; au large pkyllum propinquum. de Cruz Bay No. 2086 (var. imbi- cilla); No. 2095, No. 1917. St. Croix: Le port de Christiansted; St. Croix 1892. St. Thomas. Repartition géographique. Z,. /^ropmguwwi a été recueillie ä Porto- Rico : Santurce, San Juan, Ile Culebra (Howe); å la Jamaiqne: Montego Bay (Howe); elle vit également ä la Barbade, ainsi qu'en témoigne un échantillon de la collection Boergesen recueilli par Lassen; enfin, elle est connue en Floride å Key West (Hooper) et aux Bahamas (Howe). 9. Lithophyllum (Dermatolithon) prototypum Fosl. 1897. L. prototypum Foslie, On some Lith., p. 18. 1901. Dermatolithon prototypus Foslie, Rev. syst. surv. Melob., (1900), p. 22. 1901. Goniolithon Udoteae Foslie, New Melob., (1900), p. 21. 1909. Lithophyllum (Derm.) prototypum Foslie, Alg. Not. VI, p. 49. Dermatoli- thon prototypum Foslie, Alg. Not. VI, p. 58. Dans la description de cette espéce je grouperai les caractéres de L. prototypum et ceux de L. Udoteae; ces deux espéces ne m'ont pas paru presenter de caractéres susceptibles de les distinguer Tune de l'autre ; å mon avis L. Udoteae serait une varieté de L. prototypum vivant sur algues. L. prototypum forme sur les coraux et les coquilles, et sur algues, des croiites minces, å contour lobe, montrant des stries concentriques å la marge ; ces croiites sont d'abord orbiculaires et se soudent ensuite pour former des croutes de grande étendue ; elles sont d'abord tres adhérentes, ensuite moins fermement fixées au substratum ; de nombreuses petites croiites secondaires, égale- ment lobées au bord, prennent naissance sur la premiere croüte, dont toute la surface est ornée de petites lamelles orbiculaires tres adhérentes ; en regardant avec attention la fig. 163 on verra cette disposition tres curieuse. 168 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Les conceptacles å sporanges sont peu élevés au dessus de la surface du thalle, hémisphériques, légérement déprimés au sommet, percés d'un pore visible å la loupe ; aprés la maturité des spores il reste å la place du conceptacle une cicatrice circulaire. Ils mesurent 350 å 600// de diametre, principalement 400 å 500 /y.; les sporanges mesurent 60 å 80« de longueur et 35 ä 50// de largeur. Les conceptacles å cystocarpes ont une forme plus conique et mesurent 450 å 550//. Des conceptacles de 120 å 220 /i de diametre, observes par M. Foslie sont sans doute des conceptacles å anthéridies. La structure est en rapport avec la constitution de la croute ; chacune des petites croutes secondaires est constitué par une rangée de cellules ; en coupe on observe autant de rangées qu'il existait de croutes super- posées ; on peut souvent en observer 6, quelque- fois 12. Chacune de ces rangées est formée de hautes cellules rectangu- laires pourvues chacune d'un OU deux pores ; elles mesurent le plus souvent 25 å 35/i de hau- teur et 10 å 15// de largeur et se colorent tres fortement par Tacide iodhydrique iodé ; les cellules des rangées in- férieures atteignent 40//, et plus rarement 65 et 85 /i, tandis que celles des rangées supéri- eures n'ont que 7 å 20^«. Chaque rangée de cellules est recouverte par une rangée de cellules corticales de 3 å 5// de hauteur. Comme dans toutes les espéces du sous-genre Dermatolithon, il y a une grande variation dans les dimensions des cellules suivant les rangées et méme dans une méme rangée, Les rangées, compo- sées des cellules périthalliennes surmontées de leurs petites cellules corticales, s'individualisent souvent les unes des autres aprés decalcification et dans une coupe elles sont distantes les unes des autres (fig. 164). Dans les échantillons étudiés la rangée de base ou hypothalle était formée de cellules assez semblables de forme å celles Fig. 163. Lithophyllutn (Dermatolithon) proto typiuu sur coquille de Piiiun. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 169 des autres rangées ; au contraire les autres espéces de Dermatoli- thon montrent généralement des cellules hypoLhalliennes obliques et contournées, tres curieuses. En resumé cette jolie petite espece a un aspect tres carac- téristique, lorsqu'elle est développée sur des pierres, et ne peut étre confondue avec aucune autre ; sur algues (var. Udoteae) elle a un espace plus restreint pour se développer; elle forme de petits thalles circulaires qui rappellent ceux de Lithophyllum pustulatum. On peut cependant noter plusieurs differences essentielles: tout d'abord la formation de petites lamelles å la surface du thalle, méme souvent sur des thalles de petite taille; puis, en coupe, la presence des cellules corticales surmontant les cellules de chacune 'JOuX- Fig. 164. Coupe å travers une croute complexe de Lithophyllum (Dermatolithon) prototypum. des rangées, tandis que dans l'espéce L. pustulatum il n'existe qu'une seule rangée de cellules corticales surmontant la derniére rangée de cellules périthalliennes ; enfm comme il a été dit les rangées de cellules sont séparées les unes des autres dans les preparations; les dimensions des cellules et des conceptacles ne fournissent pas de caractéres distinctifs de grande valeur. St. Jan: Cruz Bay; au large de Cruz Bay, No. 1826, 2086; entre Cruz Bay et Great St. James, No. 2143; Great Cruz Bay, No. 1782. St. Croix: Longreef 1274, sur coquille. var. Udoteae. St. J an: Great Cruz Bay, sur Galaxaura ruf^osa, No. 1832; sur Udotea flabellum, No, 1729. St. Croix: Lagune de Christiansted, sur Udotea flabellum, No. 1305 ; Port de Christiansted, sur Galaxaura rugosa, No. 1232; Little Princess sur Udotea fahellum, 1892; Christiansted, No. 1272, 170 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Repartition géographique. iusqu^ici L. prototypum n'a pas été Signale en d'autres localités que celles mentionnées ici; elle sera sans doute découverte dans les regions avoisinantes ; j'ai en effet rapporté å cette espéce un échantillon indéterminé de l'Herbier Bornet recueilli par Hooper en Floride, ä Key West. Melobesia Lmx. 1. Melobesia farinosa Lmx. 1866. Melobesia farinosa Lmx.; Rosanoff, Mélob., p. 69, pi. II, fig 3 å 5, 10 å 12; pi. III, fig. 2 ä 13; pi. IV, fig. 1, 10; pi. VII, fig. 12. 1905. Melobesia farinosa Lmx.; Foslie, Rem. north. Lith., p. 96. 1908. Melobesia farinosa Lmx. ; Foslie, Alg. Not. V, p. 16 (f. Solmsiana Falk.). Melobesia farinosa forme sur un grand nombre d'algues de petites croiites tres minces, généralement circulaires, qui montrent sur les échantillons sees des stries radiales et des stries circulaires; la surface en est quelquefois poudreuse, d'ou son nom. Cette espéce a été remarquablement bien décrite et bien étudiée par Rosanoff. Elle est, en principe, tres facile ä determiner au microscope, par un simple examen superficiel du thalle, sans faire de coupes dans le tissu, grace å la presence tres fréquente de cellules speciales nommées hétérocystes. On observe en effet que parmi toutes les fdes de cellules, certaines se sont arretées dans leur croissance et sont terminées par une cellule plus grosse que les autres (fig. 165 b, c) ; cette cellule reste souvent incolore lorsque le reste du tissu est colore par un réactif colorant, ou sinon se colore moins fortement que les autres cellules. Les files de cellules adjacentes prennent la place de la file arrétée dans son développement, d'oii il résulte, ainsi que l'a signalé le premier Rosanoff, un aspect sinueux des files de cellules. L'abondance des hétérocystes est tres variable suivant les échantillons étudiés (voir å ce sujet Foslie 1909), sans qu'il ait été possible jusqu'ici d'émettre une hypothése sur les causes qui aménent la formation des hétérocystes. Dans les échantifions des Antilles Danoises quelques uns méme ne m'ont pas montre d'hétérocystes ; d'aprés les dimensions des cellules et l'aspect du tissu j'ai cru cependant devoir les ranger dans la méme espéce, mais je les ai inscrits ä part dans la liste des localités page 173. Dans cette espéce la dimension des cellules est tres variable et varie en particulier suivant la nature du support ; c'est ainsi que sur Zostére elles sont de plus grande dimension que sur les autres supports, constatation déjå faite par Foslie; en effet dans la plupart des échantillons des Antilles Danoises, les cellules mesurent F. Børgesen: Rhodophyceæ of the Danish W. Indies. 171 7 å 15 /y. de longueur et 5 å 10// de largeur; sur Zostére elles mesurent 15 å 22// x 7 ä 12^. De méme dans des échantillons de la Méditerranée la dimension des cellules est de 12 å 20/^ x 7 å 10//, sauf sur zostére oii elle est de 18 å 30/^ x 15 å 18/^. Tout en tenant compte de cette variabilité, on remarquera cepen- dant que M. farinosa a des cellules de plus petite dimension aux Antilles qu'en Méditerranée. En resumé on peut dire que dans cette espéce la dimension des cellules, vues de dessus, sans faire de coupe, varie entre 7 et 30// et celle des hétérocystes entre 22 et åOfjt. Les cellules de M, farinosa sont de forme rectangulaire ; leurs cloisons se colorent fortement par les réactifs en particulier par l'acide iodhydrique iodé; ces cloisons sont en general situées au méme niveau dans les différentes files et s'alignent suivant des lignes concentriques (fig. 165, a, b, c; voir aussi les figures de Rosanoff). Dans les échantillons que je range avec les auteurs dans la type de l'espéce, les files cellulaires présentent une assez grande cohesion : le tissu a, par suite, un aspect compact et regulier (flg. 165 a, b) ; mais, dans d'autres échantillons les files cellulaires sont plus laches (fig. 165 c, d) ou méme paraissent couvrir indi- viduellement sur le substratum (fig. 165 e), en affectant un aspect irrégulier tres curieux. J'ai pu observer toutes les transitions entre ces types de structure si différents au premier abord et j 'arrive, pas suite å la méme conclusion que Foslie qui rangeait les thalles å struc- ture lache dans la varieté Solmsiana Falk. ^) du Melobesia farinosa. Dans la varieté Solmsiana les hétérocystes sont généralement circulaires, tandis que dans le type de l'espéce ils sont le plus souvent allonges. Toutes les descriptions qui precedent s'appliquent å l'étude du thalle vu å plat, tel qu'il se présente sur les plantes qui lui servent de support. En coupe verticale, au contraire, le tissu est forme de trois rangées de cellules, la rangée mediane étant plus grande que les deux autres, Les conceptacles å sporanges et å cystocarpes mesurent 140 å 250 /< de diametre et atteignent 300 /< dans la varieté borealis. ') Cette varieté, appelée Melobesia callithamnioides par Falkenberg 1879 et SoLMs Laubach (Corallinaceae d. Golf. von Neapel 1881) fut appelée Melobesia Solmsiana par Falkenberg (Rhodomelaceen d. Golf. von Neapel 1901. Fauna und Flora des G. v. Neapel, p. 109) pour éviter toute confusion avec le M. callithamnioides Crouan. 172 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Les conceptacles å anthéridies mesurent 60 ä 80 /i. D'aprés Ro- sanoff, les cellules qui entourent rorifice des conceptacles å spo- ranges sont un peu allongées et relevées ; ce caractére parait assez difficile å observer sur des échantillons sees. Les sporanges mesurent d'aprés Foslie 50 å 90 « x 30 å 50 n ; j'ai observe dans un thalle sur zostére, de Christiansted, des spo- ranges de 40 å 50« x 20 å 40 /i. Gomme support M. farinosa type a été signalé sur Fucus, Laminaria, Cystosira, Padina, Sargassum, Chondrus, Rhodymenia, Fig. 165. Quelques exemples de variation de structure du thalle de Melo- besia farinosa vu de dessus, b varieté type avec hétérocyste ; a, sans hétéro- cyste; d, e var. Solmsiana; c, d, formes de transition. Laiirencia, Ecklonia, Bryothamniiim, Gigartin'a, Caulerpa, Carpa- canthiis, Chaetomorpha, Cymodocea, Posidonia, Potamogeton, Thalas- sia, Enalis et Zostera. La varieté Solmsiana a été signalée par Foslie sur Peysson- nelia, sur tubes chitineux d'hydroides, sur tubes de Serpules; Sauvageau Fa recueillie sur Valonia, sur Cystosira, sur Aglaozonia aux Canaries. Falkenberg l'a récolté å Naples sur Aglaozonia. Melobesia farinosa type (avec hétérocystes ) . St. Croix: Little Princess, sur Udotea ßabellum; Cassavagarden, No. 1389, sur Udotea flabellum; Christiansted zur Zostére; Christiansteds' Lagoon, F. Børgesen : Rhodophyceæ of the Danish W. Indies. 173 sur Udotea flabelluin; Port de Christiansted, No. 1228, sur Gelidium corneum; Coakley Bay, No. 1358, sur Padina St. Crucis ; pres Ghristiansted sur coquille — ; sur Padina leg. Hansen; White Bay, No. 1555, sur Valonia macrophysa. St. Thomas: Quest de Water Island, No. 1777, sur Valonia ventricosa, profondeur 30 metres; pres de Water Island, No. 1101, sur Udotea cyathi- formis, profondeur 30 metres. St. Jan: Cruz Bay, No. 1822, sur Udotea flabellum; idem sur Halimcda discoidea, profondeur 30 metres; idem No. 1867, sur Struvea elegans, profondeur 30 metres; au large d'America Hill, No. 2014, sur Hnlimeda; au large d'Hermitage, No. 2166, sur Zonaria variegata pro- fondeur 30 metres. 2) Sans hétérocystes. St. Croix: Christiansted sur Zostére; Long P^.eei sut Penicillus capita- tus ; cote sud de I'ile, sur Halimeda incrassata, leg. Hansen; Great Ponds strand, No. 1369, sur Valonia aegagropila. St. Thomas: Port de Charlotte Amalia No. 120, sur Halophila; pres Water Island, No. 1172, sur Halimeda incrassata var simulans, profondeur 30 metres ; No. 119 sur Halophila. St. Jan: Coral Bay, No, 140 B. 3) Melobesia farinosa var. Solmsiana. St. Jan: Coral Bay No. 140 A; pres de Great St. James, No. 2087, sur Zonaria variegata, profondeur 30 metres ; au large de Cruz Bay No. 1763 B, sur Udotea flabellum, profondeur 30 metres. St. Croix: Port de Christian- sted No. 1311 sur Gelidium corneum.; Judith Fancy, sur Turbinaria trialata; Cane Bay, sur Udotea flabellum No. 1424. St. Thomas: Ouest de Water Island, No. 1173 C, sur Udotea flabellum., profondeur 30 metres. Repartition géographique. Melobesia farinosa est une espece tres commune, connue dans toutes les mers du globe; aux Antilles elle a été signalée ä Cuba, ä la Jamaique, ä Porto-Rico, ä la Guadeloupe, å la Desi- rade, å la Barbade et å la Martinique. C'est cette espéce qui a été designee par Maze et Schramm sous le nom de Melobesia confervicola. La varieté Solmsiana parait vivre dans les mers assez chaudes ; en Méditerranée elle a été signalée ä Naples (Falkenberg, Solms); å Rhodes (Nemetz in Rein- BOLD, Hedwigia, XXXVII, p. 87, 1898); dans l'Adriatique (Haugk, Wille); aux Canaries (Sauvageau); Bahamas (Howe). Aux Antilles Danoises elle est aussi commune que le M. farinosa type, 2. Melobesia (Pliostroma) Chamaedoris Fosl. et Howe, 1906. Lithophyllum Chamaedoris Foslie et Howe, New Am. Corall. alg., p. 134, pi. 90, fig. 1. 1908, Lithophyllum. Chamaedoris Fosl. et Howe; Foslie, Alg. Not, V, p. 17. 1908. Melobesia (Pliostroma) Chamaedoris Fosl. et Howe; Foslie, Pliostr. a new subg., p, 6. Cette petite espéce forme sur les Chamaedoris des crofites d'une épaisseur de 60 å 150// qui entourent plus ou moins complétement les tiges de ces algues; leur surface est lisse, et la couleur d'un rouge assez vif. 174 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Les conceptacles å cystocarpes sont convexes ou subconiques de 150 å 200/^ de diametre d'aprés les auteurs; dans les échan- tillons de M. Boergesen la dimension la plus fréquente est ISO u; la partie centrale du toit s'affaisse aprés maturité et disparait, et il reste ensuite la partie périphérique formant rebord autour de la petite cavité centrale. Comme dans tous les Pliostroma le tballe est compose de plusieurs rangées de cellules ; on peut en observer jusqu'å 12 ; les cellules mesurent 7 å 13 /^ de longueur et 8 å 10 f/ de largeur ; dans la partie périphérique, le thalle n'est forme que d'une seule rangée. Vues de dessus, sans faire de coupe, les cellules mesurent 8 å n /n de longueur et 7 å 13/2 de largeur; elles sont arrondies, toutes semblables de forme, et constituent un tissu d'aspect regulier. Par son aspect M. Chamaedoris rappellerait d'aprés Foslie Epilithon marginatum de la cote pacifique des Etats-Unis. — Le thalle est d'autre part plus épais et d'un aspect plus unique celui de M. farinosa ; vues de dessus les cellules se distinguent de celles de M. farinosa par leur forme; dans cette derniére espéce elles sont rectangulaires et sont disposées en rangées ; de plus il n'y a pas de cellules hétérocystes dans M. Chamaedoris. St. Jan: Rams Head, sur Chamaedoris annulata, profondeur 40 metres No. 1940. St. Croix: cote sud de l'ile, Mars 1892, sur Cham, annulata; White Bay, No. 1530 et 1575 sur Cham, annulata. Repartition géographique. Iles Bahamas. Position systématique du sous-genre Lithoporella. Le sous-genre Lithoporella, auquel appartient l'espéce L. at- lantica, a été d'abord place par M. Foslie dans le genre Masto- phora, puis a été considéré par lui comme un genre distinct. J'en fais ici un sous-genre de Melobesia. Pour comprendre cette maniére de voir il n'est pas inutile de rappeler les conceptions successives de M. Foslie au sujet de ces espéces, de classement difficile, pour comprendre la modification que je propose ici. Le genre Mastophora a d'abord été divisé par M. Foslie en trois sous-genres: 1) Eumastophora ; ce sous-genre réunissait les espéces å frond e membraneuse, divisée ou laciniée, peu calcifiée et par suite flexible; il y plapait les espéces: M. Lamourouxi, M. macrocarpa, M. plana et aussi M. affinis bien que dans cette derniére espéce le thalle ne soit pas divisé. F. Borgesen: Rliodophyceæ of the Danish W. Indies. 175 2) Lithoporella et Lithostrata groupaient les espéces dont le thalle est fortement incrusté et par suite cassant. Lithoporella comprenait les espéces dont le thalle est forme d'une seule rangée de cellules^), sauf dans la region des concep- tacles {M. pacifica (Heyd.) Fosl., M. melobesioides Fosl., M. con- juncta, M. atlantica Fosl.) ; il s'opposait å Lithostrata, représenté par la seule espéce M. lapidea dont le thalle est forme de nom- breuses rangées. Les sous-genres Lithoporella et Lithostrata ont été retires du genre Mastophora ; en effet å moins de modifier la definition de ce genre on pouvait difficilement y laisser des espéces formant des croutes semblables å celles des Lithothamniées ; aussi Litho- porella avait été considéré par M. Foslie comme un genre distinct de Mastophora et ayant des affinités avec Melobesia; å mon avis les Lithoporella ne peuvent pas étre séparé des Melobesia; elles représentent une simplification de structure des Pliostroma, sous- genre de Melobesia, dont le thalle est forme de plusieurs rangées de cellules et d'une seule rangée au bord. Il me parait done logique de considérer Lithoporella comme un sous-genre de Melo- besia ; il serait caractérisé par la gran deur des cellules et des con- ceptacles qui dépassent de beaucoup celles des autres espéces de Melobesia. 3. Melobesia (Lithoporelhi) atlantica (Fosl.) Lem. 1906. Mastophora (Lithoporella) atlantica Foslie, Alg. Not. II, p. 27. 1909. Lithoporella atlantica Foslie, Alg. Not. VI, p. 59. Cette espéce forme de petites croutes minces, de peu d'étendue, qui poussent parmi les Bryozoaires, sur les polypiers morts ; elle ne peut se reconnaitre å l'aspect que lorsqu'elle est fructifiée, grace å ses gros conceptacles coniques; les conceptacles mesurent 500 å i — i 800« de diametre; les sporanges ; . f ^ pjg -^gg Thalle de Melobesia (Litho- SOnt mconnus. porella) atlantica forme d'une seule Le thalle est généralement rangée de cellules. forme par une rangée unique de cellules, plus rarement par deux; les dimensions que j'ai obser- vées sont 18 å 32 /i pour la hauteur et 10 ä 25// pour la largeur; ') Dans les Lithoporella de nombreuses croutes peuvent se superposer les unes aux autres et en coupe on peut observer de nombreuses rangées ; mais chaque croute n'est constituée que par une seule rangée. 176 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. cependant des dimensions plus considerables ont été observées par M. FosLiE : 32 ä 60// de hauteur et 18 å 40// de largeur, Cette espéce rappelie d'aprés Fos lie le M. melohesioides de rOcéan Indien et de l'Archipel Malais et s'en distingue par ses conceptacles plus petits et ses cellules plus larges. St. Jan: Au large de Cruz Bay, No. 2095, 1727. Repartition géographique. Cette espéce n'a pas été signalée en d'autres localités. 4. Melobesia (Litliolepis) af finis (Fosl.) Lem. 1906. Litholepis affinis Foslie, Alg. Not. Il, p. 17. Cette tres petite espéce forme des croutes extrémement minces et peu calcifiées ; l'aspect est souvent semblable å celui d'une poussiere qui serait répandue å la surface des coquilles ou des cailloux ; å la loupe on observe des multitudes de petits thalles qui se réunissent en s'accroissant et forment alors un petit thalle de forme å peu pres circulaire, lobé aux bords ; on remarque quelquefois la formation d'un nouveau thalle dans la partie cen- trale d'un thalle ancien. Les conceptacles de forme hémisphérique-conique, mesurent d'aprés Foslie, les uns 170 å 260 /<, les autres 60 å 120 /x; les sporanges sont encore inconnus. Je n'ai pas observe de coupe verticale du thalle; d'aprés Foslie les cellules mesurent 14 a 22^ de longueur et 9 å 18// de largeur. M. affinis montre une assez grande ressemblance avec M. (L.) hermudensis Fosl. et M. (L.) Sauvageaui. Position systémaiique du sous-genre Litholepis. M. affinis, placée par Foslie dans le genre Litholepis me parait devoir ét re rattachée aux Melohesia, en ne voyant en Litholepis qu'un sous-genre. M. Foslie (New Lith. 1905, p. 5) avait d'ailleurs insisté sur les relations de ces deux genres: en particuher les conceptacles ä sporanges sont semblables. Au point de vue de la structure, les espéces du genre Litholepis ont un thalle forme d'une seule rangée de cellules ; cette structure peut å mon avis resulter d'une simplication de celle de certaines espéces comme M. farinosa ou M. Lejolisii dans lesquelles le tissu sterile est compose de 3 rangées de cellules seulement, dont deux tres petites ; autour d'un conceptacle le nombre des rangées augmente dans le genre Melobesia de méme que dans le genre Litholepis. Litholepis pourrait done étre considéré comme un sous-genre de Melobesia caractérisé: 1) par sa nature saxicole 2) par son F. Børgesen : Rhodophyceæ of the Danish W. Indies. 177 thalle monostromatique 3) par la superposition de croütes les unes au dessus des autres. Les espéces de Litholepis connues jusqu'ici sont : M. (L.) cas- pica Fosl., M. (L.) hermudensis Fosl., M. (L.) Sauvageaui FosL, M. (L.) indica Fosl, Le sous-genre Litholepis a certains caractéres communs avec Lithoporella que je considére également comme un sous-genre de Melobesia; la structure est monostromatique, et il y a super- position de croütes dans les deux cas. Mais dans le sous-genre Lithoporella les conceptacles sont beaucoup plus gros, les cellules sont plus grandes et le thalle plus épais. St. Jan: Au large d'America Hill, No. 2072; No. 1967 (profondeur 16 brasses) No. 2104. St. Croix: Northside, sur roches exposées, No. 1468; Longford. Repartition géogra phique. M. affinis n'a pas été signalé en d'autres localités. Porolithon. 1. Porolithon mamillare (Harv.) Lem. var. occidentalis Fosl. 1847. Melohesia mnmillaris Harvey, Nereis australis, t. XLI, p. 109. 1906. Goniolithon mamillare Harv.; Foslie, Alg. Not. II, p. 15 (f. occiden- talis Fosl.). 1909. Gon. mamillare Harv.; Foslie, Alg. Not. VI, p. 10. Les échantillons de P. mamillare des Antilles Danoises for- ment des croütes lobées au bord surmontées de nombreuses petites épines cylindriques de ^/4 de mm. å 1 mm. Va de hauteur environ. Sur la premiere croüte il y a souvent formation de petites la- melles orbiculaires, formées (?a et lå au milieu des épines, et qui Yig. 167. Coupe verticale du thalle n'adhérent pas complétement å de Porolithon mamillare. la croüte. Les conceptacles sont tres gros, coniques, renflés dans leur partie mediane ; leur diametre atteint 1 '^^^,4 environ. En coupe, le tissu est forme de grosses cellules å parois minces, peu colorées par l'acide iodhydrique, elles sont disposées irréguliérement et mesurent 10 å 20/^ de longueur et 7 ä lb fx de largeur; l'hypothalle est représenté par la rangée basilaire de cellules, soit peu diflérentes comme forme et comme dimension des autres cellules du tissu, soit plus allongées (20 å 22^ x 12//). Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 12 178 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Dans les prolongements en forme d'épines qui surmontent la croute, les cellules ont å peu pres la méme dimension que dans la croute: 5 å 15//, principalement b k 1 /j de longueur. Por. mamillare var. occidentalis se différencie peu, d'aprés FosLiE, de P. mamillare type, des cotes d'Afrique. Cette espéce était placée par Foslie dans le genre Gonioliihon, genre non homogene dans lequel les espéces présentaient des types de struc- tures tres varies. Par l'irrégularité de son tissu, cette espéce me parait, ainsi que P. Boergesenii, étre mieux placée dans le genre Porolithon, å coté de P. Reinholdi. St. Jan: Au large de Cruz Bay, No. 2095, 1879 et No. 1826 (échan- tillons abimés) ; au large de l'Hermitage, No. 2181. St. Croix: Northside sur roches exposées, No. 1468 — idem récolté en 1892. St. Thomas: No. 1030. Un échantillon de Quenstedt de 1848 appartient å cette méme espéce. Repartition géographique. Un échantillon indéterminé de l'herbier BoRNET, de Key West, Floride (herb. Farlow), appartient ä cette espéce. Cette espéce vivrait également aux Iles du Cap Vert (Challenger Exp., DicKi 1875 et 1877); au Cap Vert ä St. Jago (Harvey 1847); ä St. Vincent; ä Algoa Bay (Bowerbank in Harvey 1847), sur la cote africaine; au Brésil: å Bahia (Harvey 1847). Peut-étre faudra-t-il revoir certaines des localités signalées par Harvey, en particulier celles de Port Famine (Terre de Feu) (Darwin in Harvey 1847). L'espéce signalée å Tongatabu dans l'Océan Pacifique (Dickie) est le L. erubescens Fosl. 2. Porolithon Boergesenii (Fosl.) Lem. 1901. Goniolithon (Herpolithon) Boergesenii Foslie, New Melob. p. 19. 1907. Goniolithon (Hydrolithon) Boergesenii Foslie, Alg. Not. III, p. 20 (var. africana Fosl.). Les échantillons recueillis par M. Boergesen montrent cette espéce å divers etats de développement ; l'un d'eux forme une croute d'environ 3 mm. d'épaisseur développée sur une tige de corail ; la surface en est irréguliére ; d'autres, plus ages, forment, sur des massifs de polypiers, des croutes mamelonnées ainsi qu'on le voit sur la fig. 168. L'algue jeune peut former une croute unie, ainsi qu'en témoignent les échantillons des Bahamas distribués par Howe (North American Marine Algae). On a Signale une certaine variation dans l'aspect de cette espéce, suivant la nature du substratum ; il arrive quelquefois que des thalles de Bryozoaires se développent sur des croutes de P. Boergesenii et que celui-ci recouvre å son tour les thalles de Bryozoaires ; il s'ensuit que l'algue présente des aspects variables et que la structure peut se trouver tout å fait altérée. Borgesen: Rhodophyceæ of the Danish W. Indies. 179 Ainsi que l'a remarqué Foslie, le tissu hypothallien est repré- senté par une seule rangée de cellules étroites, placées cote å cote, de 20 å 25// de longueur et 8// de largeur. Le tissu périthallien Fig. 168. Croütes de Porolithon Boergesenii. ^iOf. est forme de cellules tres variables de forme, ici rectangulaires, lå ovoides, disposées de telle sorte qu'il est difficile de suivre l'enchainement des cellules constituant chaque file verticale. Les cellules mesurent 7 å 18// de longueur et 8 å 12// de largeur; quel- ques cellules plus grosses de 20 å 25 /< X 18 å 20/« sont dispersées 9a et la dans le tissu. Les cellules prennent, suivant les regions du thalle, une coloration plus OU moins vive sans l'influence du réactif colorant, de sorte que dans son en- semble le tissu est traverse par des zones de coloration variable. P. Boergesenii rappelle beaucoup Por. Reinboldi de l'Océan Pacifique, par son tissu irrégulier, son hypothalle forme d'une seule rangée de cellules, et par la presence au milieu du périthalle de grosses cellules disséminées. Les caractéres suivants permettent de les différencier : 1) Les cellules de l'hypothalle sont plus petites dans P. Rein- boldi (16 å 22/«x 10 å 20//). 12* Fig. 169. Coupe verticale å travers le thalle de Porolithon Boergesenii; b, hypothalle. 180 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 2) Les cellules du périthalle sont, dans l'ensemble, plus grandes dans P. Reinboldi (15 å 24// x 6 å 15 f<). 3) Il n'existe pas de zones de coloration visibles dans le tissu de P. Reinboldi aprés action des réactifs. 4) On trouve fréquemment la presence d'écorces anciennes dans le tissu de P. Reinboldi. 5) Les conceptacles å sporanges mesurent 300 å 400 fji de dia- metre dans P. Boergesenii et 350 å 700,« dans P. Reinboldi. St. Croix: Plusieurs échantillons, en particulier l'un de Long Reef, Baie de Christiansted, No. 1272. Repartition géographique. En dehors des Antilles Danoises P. Boergesenii a été signalé aux Iles Bahamas (Howe), å la Barbade (échantillon de Mile Vickers 1902 in herb. Bornet et voir aussi Foslie 1901, p. 21). La presence de cette espece a été signalée sur la cote africaine ä San Thome (Golfe de Guinée) par Foslie (1907) et Hariot (1908) d'aprés les échantillons du Museum d'Historie Naturelle de Paris récoltés par M. Gravier. Ainsi que je I'ai dit plus haut (p. 149) ce qui reste actuellement de réchantillon ne permet plus de l'étudier, et de savoir si contrairement aux données que Ton posséde sur les affinités des étres du Golfe de Guinée, P. Boergesenii y est réellement représenté par une varieté africaine. 3. Porolithon pachydermum Fosl. 1904. Lithophyllum oncodes Fosl, f. pachyderma Fosl., Alg. Not. V, p. 5. 1909. Lithophyllum (Porolithon) pachydermum Fosl., Alg. Not. VL P- 41 (f. nexilis Fosl. et Howe). Cette espéce se développe sur les coraux et les pierres et y forme des croütes minces dont l'aspect n'a rien de caractéristique et peut étre confondu facilement avec d'autres espéces par exemple L. propinquum, Par. oncodes, L. inter- medium jeune etc. Les conceptacles å sporanges sont convexes, peu saillants, de 150 å 250 /i vue de la surface ; les sporanges mesurent 60 ä 70// de haut et 30 å 40 // de large. Les conceptacles å cysto- carpes sont convexes, de 200 å 300/« de diametre. En coupe on observe å la base un hypo- thalle peu développe forme de cellules courtes qui mesurent' 8 ä 17/^ de longueur et 4 å 10/« de largeur. Le périthalle a un aspect compact; les cellules sont petites, larges par rapport å dermum montrant jg^j, hauteur et généralement tres serrées ; on un groupe de 5 gros- , . i i . • +• „ ses cellules. peut cependant observer dans certames parties Fig. 170. Coupe ver- ticale de la croüte de Porolithon pachy- F. Børgesen: Rhodophyceæ of the Danish W. Indies. 181 (fig. 170) des files séparées les unes des autres; les cellules mesurent 4 å 8/i ou Så 11 fj. de hauteur et 5 å 12// de largeur. Au milieu du tissu existent Qa et lå de grosses cellules, disposées par groupes de 8; elles sont bien visibles et mesurent 17 å 20// x 8 å 15//. La presence de ces groupes de cellules différencie cette espéce de toutes les autres especes des Antilles Danoises. Par rapport aux espéces des regions plus éloignées, elle montre des affinités evidentes avec Por. oncodes de l'Océan Indien et de l'Océan Pacifique (Funafuti, Puamotou, Sumatra, N^"« Guinée). Les deux espéces se difTérencient par un certain nombre de caractéres ; les grosses cellules sont dans L. oncodes par groupes de 3, 5 ou plus rare- ment 8 ; les cellules du tissu sont dans l'ensemble plus hautes et moins larges. St. Jan: Cruz Bay; Great Cruz Bay No. 1782. Des échantillons de la collection de M. Boergesen et provenant de Quenstedt, 1848, sans localité, doivent étre rapportés å cette espéce. Repartition géographique. P. pachydermum a été signalé aux Bahamas (Howe) (f. nexilis) et ä la Jama'ique. Un échantillon de L. inter- medium de la Barbade récolté par Lassen, de la collection Boergesen recouvre une croute de cette espéce. Bibliographie. Collins. The algae of Jamaica. Proceedings of the American Aca- demy of Arts and Science, t. XXXVII, No. 9. Boston 1901. Foslie. 1897. On some Lithothamnia. Det Kongelige norske Vidensk. Selskabs Skrifter, 20 pages. Trondhjem 1897, No. 1. — 1900. New or critical calcareous algae. Det K. n. Vid. Selsk. Skrif- ter. Trondhjem (1899) 1900, No. 5, 34 pages. — 1901. Revised systematical survey of the Melobesiæ. D. K. n. Vid. Selsk. Skrifter. Trondhjem (1900) No. 5, 1901, 22 pages. — New Melobesiæ. D. K. n. Vid. Selsk. Skrifter. Trondhjem (1900) 1901, No. 6, 24 pages. — 1904. Algologiske Notiser I. D. K. n. Vid. Selsk. Skrifter. Trond- hjem 1904, No. 2. — 1905. Den botaniske samUng. Kgl. norske Vid. Selsk. Aars- beretning for 1904. Trondhjem 1905. — 1905. Remarks on northern Lithothamnia. D. Kgl. n. Vid. Selsk. Skrifter. Trondhjem 1905, 138 pages. — 1906. Algologiske Notiser II. D. Kgl. n. Vid. Selsk. Skrifter. Trondhjem 1906, No. 2. — 1907. Algologiske Notiser III. D. K. n. Vid. Selsk. Skrifter. Trondhjem (1906), No. 8, paru 1907. — 1907. Algologiske Notiser IV. D. K. n. Vid. Selsk. Skrifter. Trondhjem 1907, No. 6. — 1908. Algologiske Notiser V. D. K. n. Vid. Selsk. Skrifter. Trond- hjem 1908, No. 7, 20 pages. 182 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. FosLiE. 1908. Nye Kalkalger. D. K. n. Vid. Selsk. Skrifter. Trondhjem 1908, No. 12, 9 pages. — 1908. Pliostroma, a new subgenus of Melobesia. D. K. n. Vid. Selsk. Skrifter. Trondhjem 1908, No. 11. — 1909. Algologiske Notiser VI. D. K. n. Vid. Selsk. Skrifter. Trond- hjem 1909, No. 2. FosLiE et HowE. New American Coralline algæ. Bull, of the New York Botan. Garden, vol. IV, No. 13, 8 pages, 14 pi. New York 1906. Harvey. Nereis australis or algae of the Southern Ocean. Londres 1847 -49. Lemoine {Mme Paul). structure anatomique des Mélobésiées (application ä la classification). Annales Inst. O céanographique de Monaco, t. II, fase. 1, 105 flg., 5 pi. Monaco 1911. Maze et Schramm. Essai de classification des algues de la Guadeloupe, 2éme edition. Basse-Terre 1870—1877. RosANOFF. Recherches anatomiques sur les Mélobésiées. Mém. S o c. imp. Sc. nat. et math, de Cherbourg, [2], II, XII, 112 pages, 7 pi., 1866. Weber et Foslie. The Corallinaceae of the Siboga Expedition. Siboga Expeditie LXI, 16 pi., 34 fig. texte. Leyden 1904. Subfam. 2. Corallineæ. Amphiroa Lamx. 1. Amphiroa rigida Lamx. Lamouroux, I. V. F., Histoire des Polyp, corall. flexibl., viilg. nommcs Zoophytes, Caen 1816, p. 297, tab. XI, fig. 1. Zanardini, G., Iconographia, vol. 3, p. 79, tab. 99, fig. B. Areschoug, I. E., Corallineæ in J. Agardh, Spec. Alg., vol.11, pars I, p. 532. Solms-IjAubach, Die Corallinenalgen des Golfes von Neapel, p. 6, tab. 1, figs. 1, 11 (Fauna u. Flora d. Golf. v. Neapel, 4. Monogr. 1881). Yendo, K., CoraUinae verae Japonicae, 1902, p. 6, pi. I, figs. 5—6, pi. IV, fig. 4; Revised List of Corallinæ, 1905, p. 3. Weber- van Bosse, A., CoraUinae verae of the Malay Archipelago (in A. Weber- van Bosse and M. Foslie, The CoraUinaceae of the Siboga-Expedition, 1904). var. Alltillana no v. var. A forma typica præcipue differt, planta majore, cæspitibus usque ad 6 cm. altis, ramificatione magis regulariter dichotoma, angulis sæpe obtusis. The specimens found were growing in large, dense tufts, about 6 cm. high. They are fairly richly ramified, and the rami- fication is mostly a very regularly dichotomous one (Figs. 171 and 172). The filaments are thickest in the lower part, about 1 — 1,5 mm,, F. Børgesen : Rhodophyceæ of the Danish W. Indies. 183 Fig. 171. Amphiroa rigida Lamx. var. Antillana nov. var. Part of a regularly dichotomous thallus. (About 2 : 1). and taper evenly to the sum- mit where often the diameter scarcely reaches half the length of the above mentioned size. In the basal part the colour of the dried specimens is a ligth red-violet, towards the top almost white with a blue-violet tinge. The branches are spread- ing, the angle of the dicho- tomy being mostly obtuse, though sometimes acute. The joints are long, often reaching a length of more than one cm., cylindrical, and in their upper end, bifurcate, the nodes often (not always) occurring at rather a long distance above the dichotomy, one or sometimes even 2 mm. above it. In the upper end of the frond the dichotomy often does not occur, but the filaments are divided by nodes in a similar way as that found in the ramified parts of the thallus. Of the illustrations I have seen of this species my plant seems to come nearest to the above mentioned figure of Zanardini (Fig. B 1), but the ends of the branches of my plant are less tapering and not so curved as the ones in Zanardini's figure. From SoLMS - Laubach's description (1. c. p. 7) my plant seems to differ some- what. He says: "Sie zeich- nen sich durch unregelmässige Verzweigung und durch spitzwink- lige, wenig divergente Richtung der Aeste aus, daher denn stets kompakte dichte Rasen gebildet werden". As described above Fig. 172. Amphiroa rigida Lamx. var. Antillana nov. var. Part of a more irregularly ramified thallus. (About 2: 1). 184 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. my plant has just a fairly regularly dichotomous ramification, and the angle between the branches is often obtuse. Judging from Yendo's figure (1. c, pi. IV, fig. 4) the Japanese plant seems also to be more irregularly ramified and to form more compact tufts than the West Indian one. As to the anatomy I found it agreing very well with M™^ Weber's excellent description. In the joints the central strand consists of two rows of long cells, alternating regularly with one row of short cells. The long cells have a length of about 100//, the short ones of about 20 // only. The cortical tissue consists of several layers of short cells, shortest at the periphery. In the young thallus the cortex consists only of a few layers of cells, in the older one, on the other hand, of several, because the cortical layer increases, as the plant grows older, in thickness (comp. Solms- Laubach, 1. c). As mentioned by this investigator and described more particularly by M™^ Weber the nodes of Amphiroa rigida consist of two rows of cells (Fig. 173). The cells in these rows are of nearly the same size and have thick walls, except in the upper and lower ends where they meet the cells of the central strand. Here the transverse walls are horizontally placed while the cells in the middle of the node meet each other with oblique walls, being in this way more firmly connected. As suggested by M™*^ Weber this might, perhaps, help to increase the strength of the node. A good illustration of the node is given by Yendo in "Corallinæ veræ Japonicæ", pi. 1, figs. 5 — 6. To judge from Harvey's description of Am- phiroa fragilissima in Nereis, part II, p. 85 the plant he has had before him seems to be the same as the present one. Harvey's description seems in any case quite to agree with my plant; but, in order to settle exactly their identity, an examination of Harvey's plant is of course necessary. Harvey's closing remark that it is "an exceedingly fragile species, of which it is almost impossible to preserve more than broken fragments" is also quite in accordance with my plant, this being too very fragile. Most probably this quality has induced Harvey to refer his plant to Amph. fragilissima having not noticed the most Fig. 173. Am- phiroa rigida Lamx. var. Ant Ulan a no v. var. Part of the node show- ing the acute ends of the cells. (About 270:1). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 185 characteristic of this species: the swollen padlike ends of the joints, pointed out very clearly in Linné's short diagnosis which runs^): "C. dichotoma, articulis fdiformibus divaricatis, apice basique latioribus" and described later on by Lamouroux in Hist. d. Polyp. Corallig. flexibl., p. 298 (first quoted by Harvey) in this way: "articulations cylindriques avec un renflement en forme de boulet å leurs extrémités". In Ellis and Solander's description of their Corallina fragilissima (in Nat. Hist. Zoophytes 1786, p. 123, pi. 21, fjg. d) this character is not mentioned. Their diagnosis of the species runs verbally : "Corallina dichotoma, articulis cylindricis, æqualibus lævibus ramis erectis". This dia- gnosis agrees perhaps best with Amph. rigida the padlike swollen ends of the joints being not mentioned, but the upper bifurcate ends of the joints characteristic of this species are neither mentioned, and if we examine their figure the nodes except one are drawn at the dichotomy. As an examination of Ellis and Solander's specimens is not possible, their collections, as men- tioned earher (comp. p. 89), most probably not existing any longer, it seems to me the best course to regard Amph. fragilissima and Amph. rigida in the sense of Lamouroux and this the more so, as Linne's short, but striking diagnosis of Corallina fragilissima does not leave any doubt as to the plant he had before him. This species has been found only once. It was growing in shallow water between Cymodocea manatorum and other sea- grasses in a place somewhat sheltered by coral reefs. St. Croix: Rust up Twist. Geogr. Distrib. : Mediterranean Sea, West Indies, Japan. 2. Amphiroa fragilissima (L.) Lamx. Lamouroux, I. V. F., Histoire des Polypiers corallig. flexibl. vulg. nomm. Zoophytes. Caen 1816, p. 298. Areschoug, I. E., in J. Agardh, Spec. Alg., vol. 2, pars 1, 1851, p. 531. Weber- van Bosse, A. and M. Foslie, The Corallinaceæ of the Siboga-Expedition, Leiden 1904, p. 89, pi. XVI, figs. 1, 2, 5 (ubi synomyna pluria). KOtzing, F., Tabulæ Phycologicæ, vol. 8, pi. 39, flg. 1. Corallina fragilissima L., Systema nat., ed. 12, vol. 1, p. 1305). Ellis, J. and D. Solander, Zoophytes 1786, p. 123, pi. 21, fig. d? (comp, remarks above). Amphiroa debilis Kiitz., Spec. Algarum, 1849, p. 700. Harvey, W. H., Nereis Bor.-Am., Part II, 1853, p. 86. ^) LiNNÉ, Systema Naturae. Editio duodecima reformata. Holmiæ 1767. Tom. I, Pars II, p. 1305. 186 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The specimens found seem to agree very well with the de- scription given by M™*^ Weber and quoted above. The most characteristic feature of this species is that the long cylindrical joints are swollen padhke at both ends in the older parts of the thallus (comp, the fig. b of Kützing, 1. c). As pointed out by M^^^ Weber the central strand consists of a variable number of rows of long cells, interrupted by one or two rows of short cells. In the specimens examined by me I have found 4 — 6 rows of long cells, their length varying from about 55 — 90//, that of the short ones from 15 to 30;/. The nodes have nearly the same anatomical structure as that found in the joints, only that the walls of the cells are somewhat thicker and not calcified. M=^^ Weber has given a very fine illustration of the node (1. c). The conceptacles form small, roundish, prominent cushions along the sides of the joints. I have only found tetrasporic plants. The tetrasporangia are about 50 /r/ long and 25// broad and often taper upwards in such a way that the uppermost spore has a conical shape. Having examined the authentic specimens of Amphiroa ciispi- data and A. cyathifera and having found that their anatomical structure does not differ from that of Am. fragilissima M™^ Weber comes to the conclusion that these two species are only forms of the present plant. When stating this M"^*^ Weber adds : "I do not attach great importance to this point, whether specimens are more or less slender, if they agree on all other points". I share this view with M™^ Weber especially as my plants differ much in this respect the varying strength of the plants seeming to originate from the locality in which the plants are found. This is easily illustrated by an example. Specimens found near Cruz Bay, St. Jan, growing in an exposed place where the waves constantly dashed the plants, form very compact, dense tufts ; they have comparatively short and thick joints, the diameter of which in the middle of the thallus reaches a length of about 460//. On the other hand specimens from sheltered localities and those growing between and protected by sea-grasses are more slender, forming loose and open tufts, with much longer and thinner joints, their diameter reaching only a length of about 190/^. This species is very common along the shores of the islands and occurs both in sheltered and exposed localities, in shallow water and in deep sea down to a depth of 10 fathoms or even more. It often grows abundantly upon coral reefs and here, F. Børgesen: Rhodophyceæ of the Danish W. Indies. 187 together with Jania adhærens and Corallina cubensis, covers large extensions. It is a favoured refuge of many small algæ which find a comparatively quiet growing place among its rigid filaments. Besides many red algæ, e. g. Hypnea, Spyridia etc., Cladophoropsis membranacea especially settles itself here and often grows so vigorously here that it quite covers the host plant and together with it forms quite thick carpets on the rocks over which the surf constantly breaks. The small forma reducta of Caulerpa racemosa, mentioned in Vol. I, p. 151 was found in such a locality growing between Amphiroa fragilissima and in Fig. 123 in the same volume the var. occidentalis of Caulerpa racemosa is shown creeping between the densely felted filaments of this alga. It has been collected with tetraspores in January — March. Geogr. Distrib. : West Indies, Indian Sea. Corallina (L.) Lamx. 1. Corallina cubeusis (Mont.) Kiitz. emend. KüTziNG, Tabulæ phycologicæ, vol. 8, p. 37, pi. 77, figs, e, f (non fig. d). Jania cubensis Mont, in Kützing, Species Algarum, 1849, p. 709; MoNTAGNE, Sylloge gen. specierumque Cryptogamarum, 1856, p. 429. Up to the present day this species has been considered a doubtful one and it cannot be denied that the description of MoNTAGNE is, indeed, very poor and even misleading. It is described previously in Kützing's *'Species Algarum"; the diagnosis, the same, that is found in Montagne's "Syl- loge", 1849, p. 429, reads verbatim: "J. intricata, subsetacea, filiformis, teres, al- terne ramosa vel subdichotoma, ramis subpinnatis, pinnis ciliiformibus paucis patentibus subulatis ; articulis elongatis, diametro 4 — 6 plo longioribus, primariis clavatis, pinnarum cylindricis. Alt. ^2"". — Cuba (v. s.). — "Spec, dedit cl. Mon- tagne", is added by Kützing. This description might agree in some fj^") Km™" Habf o"1 points with my specimens, but it disagrees plant. (About 6 : 1). 188 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. absolutely with my plant, with its mostly opposite branches, when it is said in the diagnosis: "alterne ramosa vel subdichotoma". Thus an examination of the original material was highly desirable, and I am greatly indebted to M«"^ Weber for the per- mission to examine the original material sent by Momtagne to KüTZiNG and preserved in his herbarium, now in the possession of Mn^e Weber. This specimen has also a special interest on account of the fact that the only existing illustration of this species, namely that in Kützing's 'Tabulæ" (1. c), is based upon it. After the examina- tion of the material it at once became evi- dent that it was a mixture of two spe- cies present in nearly the same quantity, namely a form of the plant which I in a fol- lowing page call Jania adhaerens and another plant, the present one, for which I keep the name cubensis. It is interesting to see that KtJTZiNG very correct- ly has illustrated both species, his fig. d re- presenting Jania ad- Fig, lib. Corallina cubensis (Mont.) Kütz. Upper r,^.„._,_ „,i,-i„ fi„„ ^ part of a plant with more or less verticillated naerens wnne ngs. e branches and a tetrasporicconceptacle. (About 16:1). and / are Corallina cubensis. Before entering upon a description of this plant I further want to point out that in my specimens, too, Jania adhaerens is often abundantly present. Besides, Corallina cubensis also, often grows intertwisted among Amphiroa jragilissima. After these introductory remarks I shall proceed to give a description of the plant based upon my own material. Corallina cubensis grows upon rocks and corals and forms low dense tufts about 1 — 2 cm. high, often spreading widely. The slender filaments are densely crowded, fastigiate and mixed up together. The branches issue as a rule immediately below the nodes (Fig. 174), but the ramification is very irregular. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 189 As a rule it is opposite, but some- times 3 — 5 or more verticillated bran- ches are found (Fig. 175, 176). These branches are generally, of a very- different strength, some being vigo- rous, others dehcate. Now and then too, a single branchlet is issued from each joint or they are quite destitute of branches. And what especially contributes to make the ramification irregular are the many adventitious branches (Fig. 177). These often grow out below the ordinary branches, but they may also issue almost every- where from the joint e. g., as shown in Fig. 177, from the middle of the joint. Some of the branches, the most vigorous, grow out to main filaments like the mother-branch, but most of them become short branch- lets only. These branchlets are un- divided, or they may bear a single or a few opposite branches. The branchlets taper evenly upwards to their apex. At their base the branchlets are about 100 « thick, at their upper end they often scarcely reach 35/i in diameter. In the main filaments the joints are about 180« thick, somewhat thicker in their upper end, thinner in the lower one ; their length reaching 600^« or more. Once in a specimen I found a few of the branchlets ending in small attachment discs (Fig. 178). Fig. 177. Corallina cuhensis (Mont.) Kiitz. Joints 'Y\\q base of the with adventitious branches. Drawn from a decal- cified specimen. (About 18:1). plant consists of pro- Fig. 176. Corallina cubensis (Mont.) Kiitz. Summit of a slender plant. (About 18: 1). 190 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. strate decumbent branches, fastened to the substratum by means of haptera. As to the anatomy the central strand in the joint commonly consists of 4 rows of cells; these are about 100 /i long and about 12 /J. broad; the cells in the nodes are almost of the same size, longest in the middle, and growing shorter near the periphery (Fig. 179). Tetrasporic conceptacles (Fig. 175, 180) have been found now and then. These are urn-shaped and are produced in the upper Fig. 178. Corallina cu- bensis (Mont.) Kütz. Branchlets ended with small discs. (About 20:1). Fig. 179. Corallina cuben- sis (Mont.) Kütz. Longi- tudinal section of the node. (About 200 : 1). joint of the branchlet. They are rarely destitute of ramuli (horns), mostly bearing 2—5 ramuh verticil! ately placed round the middle of the conceptacle. The conceptacles are about 450 /i long and 270// broad. The tetrasporangia are transversely divided, nearly cylindrical or somewhat curved with rounded ends, about 180// long and 70// broad. Corallina cubensis seems to be rather common along the shores of the islands ; it is found in depths from 5 — 10 fathoms of water and occurs often in the open sea in places where strong currents prevail. It is generally associated with other corallineous algæ, e. g. Amphiroa fragilissima and Jania adhaerens. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 191 St. Croix: off Frederiksted, in White Bay. St. Jan: off America Hill and in several places in the sound between this island and St. Thomas. Geogr. Distrib. : West Indies. Fig. 180. Corallina cu&ensi5 (Mont.) Kütz. Transverse section of a tetrasporic conceptacle. (About 80:1). Jania Lamx. In various papers Yendo ^) points out that the most charac- teristic feature l3y which Jania is distinguished from Corallina is the dichotomous ramification of the filaments as against the pin- nated branches in Corallina. I agree with Yendo in this point of view. 1. Jania pumila Lamx. Lamouroux, I. V. F., Hist. Polyp, corallig. flexib., 1816, p. 269, pi. 9, fig. 2. Areschoug, I. E. in J. Agardh, Spec. Alg. vol. II, p. 559. 1) Yendo, K., Principle of systematizing Corallinæ (The Botanical Maga- zine, Tokyo, 1905, vol. XIX, p. 123) and A revised list of Corallinæ (Journal of the College of Science, Tokyo 1905, vol. XX, p. 2). 192 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Corallina pumila (Lamx.) Kütz., Tab. Phycol., p. 39, tab. 83, fig. 1. Hauck, f., Meeresalgen von Puerto-Rico in Engler, Bot. Jahrb., 9. Bd., 1888, p. 465. Heydrich, F., Beiträge zur Kenntnis der Algenflora von Ost-Asien (Hedwigia 1894, p. 301). This little plant grows epiphytically upon larger algae, e. g. Turbinaria and Zonaria. It is fastened to the host-plant by means of a small roundish disc. In the specimens examined by me the disc was about 400// in diameter. From the surface of this disc the erect filaments arise; at their base, where they are attached to the disc, a node is always present. As the specimens showed some differ- ences according to their growing upon Turbinaria ov Zonaria I wish to describe them separately and begin with those upon Turbinaria (Fig. 181). This was growing in a very exposed place at Judith Fancy on the north side of St. Croix and on account of this the specimens of Jania had also a Fig. 181. Jania pumila Lamx. Habit of a plant rather robust appea- with cystocarpial and antheridial conceptacles ^^ growing upon Turbinaria. (About 25:1). rance. The erect filaments are of very variable size and development. Some of them consist of a single joint which on its top bears a conceptacle, others are longer, a few times dichotomously divided, ending in conceptacles, if they are not throughout vegetative. In the basal part of the filaments the vegetative joints are mostly oblong-cuneate with broadly rounded top and very atten- uated base, in the upper part nearly cyUndrical, tapering some- what to both ends. The first mentioned joints are about 200// long, about 150 /i broad at their upper end and 70 /^ at their base, but much larger ones occur; the more cylindrical joints in F. Borgesen: Rhodophyceæ of the Danish W. Indies. 193 the upper ends of the filaments are about 250//. long and about 80 /i broad in the middle. The antheridial and cystocarpic conceptacles occur together in the same plant (Fig. 181), while the tetrasporic conceptacles occur in separate plants. As pointed out by Hauck (1. c.) the tetrasporic and female conceptacles are developed in the basal joint in the uppermost dichotomy. This joint is cuneate of shape ; it is large, of very variable length, often more than 800 /^ long; the breadth, at the upper end, where the conceptacles are found, seems on the other hand less variable, about 250 /i. In the tetrasporic conceptacles (Fig. 182) the hornlike prolongations at both sides of the conceptacles mostly consist of two nearly cylindri- cal joints, while in the female concep- tacles these horns consist only of a single joint. But having seen so very few plants I dare not say that this is always the rule ; in the female conceptacle the joints in the horn are about 60 — 70// broad and about 300 /i long, while in the tetrasporic the lowest joint in the horns is about 70 fi broad and 400/« long, the upper joint a little thinner and shorter, about 230/« long. The joint with the antheridial conceptacles are ovate— spindleshaped and of smaller size than the tetra- sporic and female conceptacles; they are about 250« long and 140// broad. They are formed in the uppermost joint of a branch; the few antheridial filaments I have seen in the form from this locality have all been short, consisting only of the antheridial joint or, besides, of a single vegetative joint below. While I have had very few specimens growing upon Turbi- naria at my disposal, I have collected a specimen of Zonaria lobata at the shores of St. Croix upon which numerous specimens of this small Jania were present (Fig. 183). Unfortunately the exact locality of this plant is not known, but most probably it Fig. 182. Jania piunila Lanix. Longitudinal section of tetra- sporic conceptacle of specimen found upon Turbinaria. (About 75: 1). Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 13 194 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. is from a more sheltered place. Compared with the above des- cribed specimens these are comparatively slender with longer branches. The erect filaments are several times dichotomously branched. The antheridial conceptacles occur in the ends of these long branches as against the often sessile ones in the form described above. The tetrasporic conceptacles (Fig. 183) have longer horns consisting of 4 joints ; female conceptacles I have not seen. As to the anatomy, the cells in the central strand are of about the same length as those in the nodes. X Fig. 183. Jania pumila Lamx. Specimen found upon Zonaria. (About 20 : 1). In referring this plant to Jania pumila I may point out that I have not been able to make any comparisons with original material ; to arrive at an exact determination this seems necessary, the more so, as the original description is very poor and the accompanying figure of no value at all. The form Kützing has illustrated differs considerably from my plant. In naming my plant /. pumila I rely upon Hauck's description ; this is based upon specimens from Puerto-Rico and seems to agree well with my plant. Hauck does not mention how far he has compared his plant with original material. The plant from Jamaica distributed in "Phycotheca Bor.-Am.", no. 799 seems to come very near to mine. This plant has only been collected a few times, but is most probably a common epiphyte upon larger brown algæ. F. Borgesen: Rhodophyceæ of the Danish W. Indies. 195 St. Croix: Judith Fancy (upon Turbinaria trialata) and another gather- ing from the same island without exactly known locality (upon Zonaria lobata). Geogr. Distrib.: West Indies, Red Sea, Indian Ocean, Japan etc. 2. Jania adhaerens Lamx. Lamouroux, I. V. F., Histoire des polypiers coralligénes flexibl. vulg. nommés Zoophytes, Caen 1816, p. 270. Areschoug, J. E., in J. Agardh, Spec. Alg., vol. II, pars 2, p. 559. Kützing, F., Tab. phycol., vol. 8, pi. 83, figs, g, h. The specimens I have referred to this old species of Lamou- roux vary considerably with regard to size, length of joints in Fig. 184. Jania adhaerens Lamx. Habit of a specimen. (About 7 : 1). Fig. 185. Jania adhaerens Lamx. Upper ends of fdaments showing the regular dichotomy. (About 20 : 1). proportion to breadth etc., but nevertheless it seems very natural to me to take them together, as transitional links are found between them and they, most probably, are nothing but variations of the same plant due to differences in habitat. The plant grows upon stones, corals or similar substrata or intertwisted among other Corallinaceæ, e. g. Amphiroa fragilissima or epiphytically upon larger algæ, especially Digenia, stems of Halimeda, Avrainvillea etc. 13* 196 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. When growing upon stones etc. it forms small dense, roundish tufts upto 1 — 2 cms. high, when epiphytic it often covers the host plants quite densely. The thallus is slender (Fig. 184). In the basal part of more vigorous plants its diameter reaches about 100 rarely up to 150^«, upwards it grows thinner and in the uppermost thin filaments the diameter reaches only a length of about 30 — 60/^. The thallus is repeatedly dichotomously ramified (Figs. 184 — 185). At the base of the branches a node is always found. The distance bet- ween the ramification is of very variable length, now long and now short, but, when long, the thallus is divided by nodes in nearly equally long joints. The length of the joints varies from 5 — 8 times their breadth. Fig. 186. Jania adhaerens Lamx. Basal parts of filaments with flat, roun- dish attachment discs. (About 60:1). The cells in the nodes are about . 200 n long and 7 fx thick ; in the joints 3 — 5 rows of long cells are mostly found ; these have nearly the same length as those found in the nodes. In the basal parts of the thallus I have found a few times some small attachment discs (Fig. 186); those are mentioned by Yendo in his paper: "Corallinae verae Japonicae (Journ. of the College of Science, vol. 16, part 2, p. 24, Tokyo 1902). Nearly all the specimens I have come across are sterile ; some few tetrasporic specimens were found growing epiphytically upon Digenia (Fig. 187). The conceptacles are urnshaped ; they are developed from the basal cell in the upper dichotomies and provided with two long branchlets often several times articulated. The conceptacles are about 300;/ long and of nearly the same breadth. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 197 In another specimen growing upon Corals some few concep- tacles were also found. These were about 240 /^ broad and 340// long, and had very long horns. As mentioned above this plant occurs both upon stones etc. and epiphytically upon larger algæ. It is found both in sheltered Fig. 187. Jania adhaerens Lamx. Specimen with tetrasporic conceptacles. (About 20:1). localities and in more exposed ones, and in shallow as well as in deeper water (about 10 fathoms or more). It is a very common species along the shores of the islands. Geogr. Distrib. : Red Sea, Indian Ocean, Japan. 3. Jania decussato-dichotoma Yendo. Yendo, K., a revised list of Corallinæ in Journal of the College of Science, Tokyo 1905, vol. XX, p. 37. Corallina decussato-dichotoma Yendo, Corallinæ veræ Japonicæ in Journ. of the College of Science. Tokyo 1902. vol. XVI, p. 25, pi. Ill, figs. 1—3; pi. VI I, fig. 34. Intermingled with other Corallinaceæ, e. g. Amphiroa fragi- lissima and Corallina cubensis I have found a few specimens of 198 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. a somewhat more robust plant than the aforementioned one. It seems to show much hkeness in shape and size to Yendo's species. In the specimens found the diameter of the joints varies from 110;/ to 175;/, their length being 3 — 5 times as long. The whole plant is rather straight and stiff. The joints in the filaments are cylindrical, except the upper- most ones in the ends of the filaments which taper much upwards, ending in acute pointed summits. The specimens found are all sterile. I wish to point out that they show much likeness to the habit-figure of Kützing's Jania tenella in Tabulæ Phycologicæ, vol. VIII, pi. 85 (fig. /), but this species is smaller; in De-Toni's Sylloge the filaments are said to be 100;/ broad. The plant was collected in rather deep water, about 10 fathoms. St. Jan: off America Hill and in the sound between St. Jan and St. Thomas off Cruz Bay. g Geogr. Distrib. : Japan. 4. Jania capillacea Harv. Harvey, W. H., Nereis Boreali-Americana, Part II, 1853, p. 84. In the Herbarium of the Botanical Museum is found an old specimen of a Jania which I think can be considered as a form of Harvey's plant. Harvey's short diagnosis runs verbally: "minute, dichoto- mous, capillary, with wide axils; branches recurved, squarrose; articulations cylindrical, four to six times as long as broad". The plant in question (Fig. 188) agrees very well with this diagnosis with the exception that the joints are somewhat shorter in proportion to their breadth, these being about 150;/ long and 350—400;« broad. A plant very similar to that from St. Croix has been distri- buted in Phycotheca Bor. Am., Nr. 150, originating from Jamaica. This plant, too, has comparatively short joints. On the other hand I have seen a small specimen belonging to the Riksmuseum, Stockholm, which seems better to agree with the diagnosis of Harvey. It was collected at Key West and determined by Farlow. The filaments in this plant are about 110« thick, the length of the joints about 5 times as long, but this plant approach- es considerably to some of the forms I have referred to Jania adhaerens. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 199 The specimen from St. Croix had tetrasporic conceptacles ; these were developed not only in the uppermost joints below the dichotorjiy, but also farther down in the plant. Perhaps we in this have a means to distinguish the two plants in question, in any case I have always found the conceptacles in the uppermost joints in the forms I have referred to Jania adhærens, but I may point out that I have seen only very few fruiting specimens. Fig. 188. Jania capillacea Harv. Part of a sterile plant and a branch with tetrasporic conceptacles. (About 15 : 1). Unquestionally Jania capillacea comes near to Jania adhærens. What especially distinguishes it from this species is the frequently obtuse angles and the arch-shaped, recurved, squarrose filaments. St. Croix (without locality) Benzon. Geogr. Distrib.: West Indies. 5. Jauia spec. On a reef in the harbour of St. Thomas I have collected a few small sterile pieces of a Jania which perhaps are referable to Jania rubens (L.) Lamx. They differ from the two preceding species by the tapering of the joints towards the ends, these being not so markedly cylindrical as is the case of these species. The thicker joints are about 150// thick and 2 — 3 times as long, the thinner about 80 — 90 // thick. 200 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. III. Ceramiales. Fam. 1. Cerainiaceæ, Subfam. 1. Spermothamnieæ. Spermothamnion Areschoug. 1. Spermothamuion investiens (Crouan) Vickers. Vickers, A., Liste des Algues marines de la Barbade (Ann. sciences nat., IX. sér., t. I, 1905, p. 64). Fie 189 Spennothamnion investiens (Crouan) Vickers var. cidaricola Børgs. ^' ■ Base of a plant. (About 175 : 1). Callithaninion investiens Crouan in A. Schramm et H. Maze, Essai de classification des Algues de la Guadeloupe, Basse-Terre 1865, p. 7. var. cidaricola Børgs. Borgesen, F., Some new or little known West Indian Florideæ (Bot. Tidsskr., vol. 30, 1909, p. 17). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 201 This beautifully purple-rose plant was found upon the pikes of Eiicidaris tribuloides, often covering these quite densely ; the tufts reach a height of ^h cm. The basal creeping filaments (Figs. 189, 190 A) are irregularly branched; they are about 30,« broad, having a very thick wall (often 8 — 10// thick). The filaments are fastened to the pikes of the Echinoderm by means of rhizoids. These are shorter or longer without any transverse walls, but having very thick peripheral walls, the lumen of the cells is, in this way, reduced to very little. At the bottom end the rhizoids for the most part broaden out to a flat, roundish, irregularly lobed disc. The erect filaments are very straight and not much branched ; the branches issue alternatingly, but seldom oppositely. The filaments are from 16 — 25// broad; the cells from 3 — 5 times as long as the diameter. The last mentioned contain many small, oblong, parietal chromato- phores more or less growing together, forming irregularly lobed, parietal plates and having several nuclei especially in the apical cell where often more than ten are to be found. Only plants with tetra- sporangia were found. These are situated terminally upon a short one-celled branchlet growing out singly (very rarely in twos) from the upper end of the mother-cell (Fig. 190 C). Only seldom the branchlet may have two cells; sometimes, too, it has a lateral sfcalk-cell with a sporangium (Fig. 190 B). The sporangia are tetrahedrally divided, ovate roundish, about 46 — 52 /i long, and 44—46/7. broad; the wall of the sporangia is very thick, 6 — 8/^ or more. Fig. 190. Spermothamnion investiens (Crouan) Vickers, var. cidaricola Borgs. A, piece of a plant with creeping and erect filaments (25:1); 5 and C, pieces of erect fila- ments with tetraspores {B, 50:1; C, 70:1). The original specimens upon which the brothers Crouan have based the description of their species were found upon Galaxaura lapidescens and Stromhiis gigas. In Schramm et Maze, "Essai de classification des Algues de la Guadeloupe" ^) ») During a stay in Paris I saw this rare book in the library of Dr. Bor- NET, and he allowed me to take a copy of it. 202 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. we find the following description: "Frondes filiformes, articulées, monosiplioniées, de couleur rose carmine se conservant parfaite- ment en herbier" and for the variety: "Fronde filiforme, articulée, monosiphoniée, beaucoup plus longue et plus rigide que l'éspéce type, de coloration rose pale". These descriptions are very poor, and any exact determination by means of them is excluded. There- fore it has been of much value to me, owing to the kindness of Mr. Paul Hariot in Paris, to be able to study an original speci- men belonging to the Museum d'histoire naturelle. This plant, growing upon Galaxaura, in nearly every respect agreed with mine. It had the same horizontal, creeping filaments fixed to the host plant with similar rhizoids as in my plant, and from these creeping filaments the erect ones grow up between those of the host plant. But while the erect filaments in my plants are only slightly branched and, as a rule, only in their upper part, the filaments in the type specimen are freely branched from near their base upwards. As mentioned above my specimens had only tetrasporangia, and this was also the case with all the plants found on specimens of Eucidaris trihiiloides collected by Dr. Th. Mortensen, who most kindly placed his material at my disposal. This species is found in deeper water only, at a depth of abouth 15 fathoms. It had ripe tetrasporangia in the month of March. St. Jan: in the sea to the north of this island. Geogr. Di strib. : West Indies. Subfam. 2. Griffithsieæ. Griffithsia C. Ag. 1. Griffithsia globifera (Harv.) J. Ag. Agardh, J., Epicrisis, 1876, p. 67. De Toni, Sylloge Algarum, vol. IV, p. 1280. Børgesen, F., Some new or Httle known West Indian Florideæ II (Bot. Tidsskrift, vol.30, 1910, p. 204). Griffithsia corallina? var. globifera Harvey, Nereis Bor.-Am., part II, p. 228, tab. XXXV A. Griffithsia glohulifera (Harv. in litt.) in Kützing, Tabulæ Phycologicæ, 1862, vol. XII, p. 10, tab. 30. Griffithsia Bornetiana Farlow, The marine Algæ of New England, p. 131, pi. X, fig. 4, pi. XI, figs. 3 and 5. As to the specific name I refer to my remarks in the paper quoted above. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 203 I This species easily known by its characteristic antheridial stands has been found in great quantities in the sea around Buck Island north of St. Croix, and in the sound between St, Thomas and St. Jan. In the North Atlantic it is known from the shores of Massachusetts down to New Jersey. Here it is a sum- mer plant, while in the West Indies it was found by me in February — March. It is almost certain that it has not been found pre- viously in the West Indies. To be sure M""^ Vickers records it in her list ^) of algæ from Barbadoes, but, as pointed out by Lewis ^'), Professor Farlow does not believe the specimens of M^® Vickers to be identical with Gr. Bornetiana. More- over Prof. Farlow himself, most kindly, has informed me by letter that he had written to Dr. Bornet on the subject and, that the latter after having seen the above-mentioned specimens found by M"^ Vickers did not think her warranted in naming them Gr. glob if era. In the above quoted paper of Lewis, edited only Fig. 191. Griffithsia globifera (Harv.) J. Ag. a, basal part of a plant and upper end of a branch, b, part of a female plant with cystocarps surrounded by pro- tecting cells, verticillate ramified hairs and dwarf shoots, (a, about 6:1; b, about 18:1). ^) Vickers, A., Liste des algues marines de la Barbade. (Ann. Sc. Nat. 9e serie, Bot. t. I, 1905). 2) Lewis, L F., The life history of Griffithsia Bornetiana (Annals of Bo- tany, voh XXIII, nr. XCII, Oct. 1909). 204 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. a few years ago, we have got a detailed description of this plant to which I refer, restricting myself here to a short description only and some figures of the West Indian plant, showing its great likeness to and small differences from the North American form. The chief difference is that the cells in the West Indian plants generally are much thicker than those of the plants from the North Atlantic. This apphes especially to the cells in the basal part of the thallus. In the West Indian form the cells are nearly oval about 2 mm. long and 1,3 mm. broad, while in the North Atlantic plant the cells are much thinner, but on the other hand much longer, nearly cyhndrical with somewhat swollen upper ends. Higher up in the thallus of the W^est Indian plants the cells are often nearly spherical, of very variable size, the larger about 1,4 mm. broad. Compared to the sizes given by Lewis, 1. c. p. 642, it is evident that the cells of the West Indian form are larger and also seem to have a somewhat different shape from the North Atlantic one, but I do not think we can lay so very much stress upon this fact, and Professor Farlow has also most kindly in- formed me that the shape and size of the North American plant vary very much, especially in the tetrasporic and sterile specimens, and as my plant, on the other hand, in its tetraspores, antheridia and cystocarps, seems to agree completely with the description of that from the United States I have referred it without any doubt to this species. The West Indian plant forms dense, semiglobular tufts, reaching a height of 6 cms. or more. It grows especially epiphyti- cally upon calcareous algæ, e. g. Halimeda, Penicillus etc., but is also found upon stones and pieces of coral at the bottom of the sea. The plant is fastened to the substratum by means of vigorous rhizoids (Fig. 191 a)^). These grow out from the basal cells, having very thick walls and being very irregularly ramified. Also from the basal end of the cells in the lowest part of the plant rhizoids grow out, but they are shorter here and not ramified. They grow downwards, attaching themselves to the upper end of the cell below, contributing in this way to the strengthening of the whole thallus (Fig. 191 a). The wall of the cells in the basal part are very thick and stratified. The thallus is repeatedly forked (Fig. 191 a) and, judging from the young stages of division I have seen, the division 1) Lewis, J. c. p. 653 points out that Griffithsia is anchored to the substra- tum either by a special attaching disc, or by a tangled mass of rhizoids. F. Børgesen : Rhodophyceæ of the Danish W. Indies. 205 often comes very near to true dichotomy, . but when exam- ined more carefully one finds that one of the young cells is always formed a little earlier and is larger than the other (comp. Fig. 192 c, d). Lewis, too, (1. c. p. 250) considers the ramification to be lateral, "true dichotomy appears never to occur". In Griffithsia corallina Kylin^) found the ramification to be lateral, and Oltmanns says in Handbuch the same for Griffithsia on the whole. As pointed out by Lewis, and according to my material also, by far the greater part of the specimens were tetrasporic. The tetrasporangia form a ring at the upper end of the cell (Fig. 192 a). As a rule three of them are found together, one of them placed termin- ally, the others later- ally upon a basal cell (Fig. 193 a, d) ; the development of this tetrasporic branch is given by Lewis. On the outside this tetrasporic ring is pro- tected by a circle of short, thick somewhat inwardly curved cells, together forming a kind of involucrum (Fig. 192 a). As pointed out by Lewis these cells grow up immediately from the cells in the main filaments (Fig. 193 a). In Griffithsia corallina Kylin (1. c, p. 116), on the other hand, describes and beautifully delineates the protecting cells as excrescences from the basal cell in the tetrasporic branch. A cell is cut off from the basal cell, and this cell is divided into two cells, the uppermost being very enlarged and becoming a protecting cell. This way ') Kylin, H., Die Entwicklungsgeschichte von Griffithsia coraUina (Lightf.j Ag. (Zeitschr. f. Botanik, 8. Jahrg., 1916, p. 99). Fig. 192. Griffithsia globifera (Harv.) J. Ag. a, part of a tetrasporic plant, b, a dwarf shoot. c and d, upper ends of main filaments showing ramification, (a, about 25: 1 ; b, about 250 : 1); c and d, about 30 : 1). 206 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. of development being rather different from what is the case in Grijfithsia globifera I again examined my material, and I found that it verified the observation made by Lewis. Fig. 1.93 b and c shows two young protecting cells. They grow out from the mother-cell in a precisely similar method to the basal cells in the tetrasporic branch. Lewis describes it in this way (1. c, Fig. 193. Gn'ffithsia globifera (Harv.) J. Ag. a, base and top of two cells of tetrasporic plant showing the large porus ; upon the lowermost cell two tetrasporic branches and two involucral cells, b and c, young involucral cells, e, involucral . cell with swollen base, d, young tetrasporic branch, f, young cystocarp with involucral cells, {a, about 80 : ], b — f, about 150: 1). p. 664): "On the side toward the stalk-cell the cytoplasm of the mother-cell is produced into a rather narrow strand, which meets a similar strand from the stalk-cell at the point where the callus-like plugs are developed". A few times I have found the basal narrow strand somewhat swollen (Fig. 193 e), but I have F. Borgesen: Rhodophyceæ of the Danish W. Indies. 207 not seen any wall or pore so it is evidently nothing else -but an accidental swelling. According to Kylin's detailed examination of Gr. corallina the present species, with regard to the development of the pro- carp etc., differs somewhat from Gr. corallina making a revision desirable. As pointed out by Kylin the chief difference is that the cell supporting the carpogonial branch in Gr. corallina cuts off another cell, this being the auxiliary one, while in Gr. globifera no such cell is cut off, the supporting cell itself acting as the auxiliary cell. Unfortunately my material is now unfit for more detailed examination having been kept in formalin for more than ten years, but my figure of the procarp, published in 1910 (1. c, fig. 20£'), seems to agree precisely with the figures in Lewis's treatise and seems to verify his description. But, of course, an examination of fresh material would be desirable. Fig. 193 / shows a young cystocarp in which the peculiar fusion of the cells in the centre of the female branchlet has taken place. From the large placental cell, resulting from this fusion, two sporogenous lobes are developed. The figure shows the involucral cells as the enlarged end-cells of the two-celled branch- lets issued from the basal cell in the procarp. Before the examination of Lewis the development of the cystocarp in Griffithsia globifera has been examined by Farlow (1. c), Spalding^) and Miss A. Smith ^). Fig. 20 D in my earlier description of the plant shows one of the large terminal cells of the male plant with the characteri- stic cap-like disc of antheridia at the summit of the cell. Farlow is the first who has described it and given a figure of it ; later it has also been mentioned by Lewis. In the West Indies I have found this species fully developed with tetraspores, antheridia and cystocarps in the months of February arid March. All the specimens were collected in rather deep sea in depths from 5 — 15 fathoms with the exception of a single specimen gathered during my first visit to the West Indies in 1892, It was found in the environs of Christianssted, St. Croix, most probably washed ashore. 1) Spalding, V. M., Development of the sporocarp of Griffithsia Borne- tiana (Proced. Am. Assoc. Adv. Science 39; 1890). *) Smith, A. A., The development of the cystocarp of Griffithsia Borne- tiana. Bot. Gazette, XXII 1896. 208 - Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Tilis species has been found near Buch Island at St. Croix in a depth of about 5 fathoms and in several places in the sound between St. Jan and St. Thomas. Geogr. Distrib. : The Atlantic coast of North America. 4. Griffithsia spec. A single specimen of a sterile plant, which I suppose to be a Griffithsia, has been dredged in the sound between St. Thomas and St. Jan, ofT Cruz Bay. The thallus of this plant is repeatedly pseudodichotomously ramified, and has in the basal part large, nearly cylindrical cells, about 300 — 400 yy thick and 7—8 times as long. Towards the summit the filaments taper gradually, the cells at the same time becoming shorter; the uppermost cells are only about 150 /z thick, the top cell, when more developed, about 100,« only. It was found in a depth of about 20 meters. Subfam. 3. Mesothamnieæ. Mesothamnion nov. gen. Habitus frondis omnino Callithamnio similis, tetrasporangiis etiam eodem modo dispositis et divisis ; difTert autem ab hoc genere corpusculis antheridiorum subcylindricis pedicellatisque et procarpiis terminalibus cellulis auxiliaribus singulis instructis. Cystocarpia ex corpusculis 5 — 6 subglobosis, carposporas con- tinentibus, composita, ramulis pluribus plus minusve involucrata. Mesothamnion caribaeum nov. spec. Planta in parte basali rhizoideis numerosis ramosis affixa; caule non corticato quoqueversum lateraliter ramoso, cellulis fere cylindricis in media parte ca. 450^ longis, 230^« latis. Rami eodem modo ramulos gerunt, ramulis pseudodichotomis ex cellulis cylindricis in media parte ca. 80,« longis, 25 /i latis compositis. Tetrasporangia sphærica triangule divisa, 45,« lata. Corpuscula antheridiorum subcylindrica, pedicellata, ca. 75// longa, 40 /i lata. Cystocarpia satis magna ex pluribus corpusculis plus minusve sphæricis et magnitudine diversis composita sunt. The thallus grows like a small shrublike tuft about 2 cm. high. It is fastened to the host plant by means of a very rami- fied root-system (Fig. 194 d). This consists, not only of the basal ramified end of the main filament, but also of several vigorous F. Borgesen: Rhodophyceæ of the Danish W. Indies. 209 filaments emerging higher up from the main stem. Like the main stem these filaments end in rhizoids often growing together to small discs. Fig. 194. Mesothamnion caribaeum nov. spec, a — c, quite young and older cells showing shape of chromatophores. d, base of a plant. {a, b, c, about 200 : 1 ; d, about 40). The basal cells in the main stem are comparatively small, but they rapidly increase in size, so that, at a short distance from the base, we find the thickest part of the main stem, the cells here reaching a breadth of 250 ft or even more ; on the other Pansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 14 210 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. hand, the cells in this part of the stem are mostly short ones, often reaching only a length of ahout 100//. From this jDlace the cells gradually taper upwards, becoming at the same time longer. In the middle of a plant the cells are about 450 /^ long and 230 ß broad ; they are nearly cylindrical, yet somewhat swol- i Fig. 195. Mesothamnion caribaeum nov. spec, a, part of tetrasporic plant. h, part of a female plant, (o, about 40:1; b, about 50:1). len at the base, tapering upwards and again a little thicker at their upper end. Near the summit of a branch in active growth the cells in the main filaments are almost quadratic, about 15// broad. In some plants a main stem can be followed through the whole length of F. Børgesen: Rhodophyceæ of the Danish W. Indies. 211 the plant, in others this is not the case as several branches are nearly equally vigorous. No cortical layer is found, but from the basal cells of the more vigorous branches a rhizoid-like filament often emerges (Fig. 194 d), growing downwards along the main stem, but generally not attached to it. In the lowermost part of the plant, as mentioned above, these rhizoids reach down to the host plant and fasten themselves to it, but higher up it may happen that they attach themselves to a branch beneath them. Fig. 196. Mesothamnion caribaeum nov. spec, a, part of an antheridial plant, b, antherial stands, c — h, development of antheridial stand. (a, about 50:1; b, about 125:1; c—g, about 300:1; h, about 450:1). The plant is much ramified (Fig. 195), the branches issuing multilaterally to all sides. As mentioned above some of the branches grow out vigorously like the main stem, but most of them are not so much developed. These smaller branches are in the same way multilaterally ramified, bearing repeatedly pseudo- dichotomously ramified branch].ets on all sides. The branchlets are longest at the base of the branches, higher up shorter and at the same time bent upwards, the whole branch in this way 14* 212 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. often getting a penicilliform appearance. The cells in these branchlets are nearly cylindrical, being in the middle of the branchlet about 80// long and 25 /^ broad. The chromatophores (Fig. 194 a, b, c) are parietal, consisting, in the quite young cells, of shorter or longer irregularly shaped plates ; in more developed cells they have the shape of a small roundish disc and finally in the old mature cells we find them like the thin, sinuate ribbons generally found in this group of algæ. One nucleus is present in each cell. Hairs are wanting; at least I have not found any in my material. Male (Fig. 196) and female (Fig. ] 95 b) plants as well as tetrasporic plants (Fig. 195 a) occurred in the collection. Jud- ging by the rather scarce ma- terial at hand the tetrasporic and the female plants are the most vigorously developed and also most common, while the antheridial plants seem to be more slender and rare. The tetrasporangia (Fig. 195 a) are spherical, lining the upper (inner) side of the filaments in the branchlets, issuing singly at the upper end of each joint. They are tetrahedrally divided. Their diameter reaches a length of about 45/7; their wall is about 2,5 /< thick. The antheridial stands (Fig. 196) are pedicellate, subcylindric- al bodies about Id fj. long and 40 /z broad; the stalk is about 30 /i long and 12 fx broad. They are found in the same places as the tetrasporangia, lining the upper side of the filaments. They originate from a cell which is richly filled with protoplasm. This cell is divided by transverse walls into 3 — 4 superposed cells (Fig. 196 c). These increase in size and, with the exception of the lower part of the basal cell which forms the stalk, are divided gradually by several anticlinal and periclinal or more Fig. 197. Mesothamnion caribaeum nov. spec. Two procarps with tri- chogynes. a, with adherent sperma- tium. (About 200 : 1). F. Borgesen: Rhodophyceæ of the Danish W. Indies, 213 irregularly arranged walls in a number of small cells or rather short filaments, the end cells of which are the antheridia (Figs. 196 d—h). The procarp occurs terminally upon short branchlets (Fig. 195 b). When fully developed it (Fig. 197) consists of a basal cell from which the carpogonial branch issues, and a sterile cell nearly opposite to it ; in the middle we find the large auxiliary cell and above it a sterile apical cell. The carpogonial branch is com- posed of _ 3 cells and the pjg ^gg, Mesothamnion caribaeum nov. carpogonium with the spec. Development of cystocarps. a, the trichop-vTip • thp last mpn- auxiliary cell is divided "in three cells, b, iricnogyne, tne last men- ^^^^ advanced stage. (About 200:1). tioned is rather robust, nearly cylindrical and very persistent. By means of staining in Mayer's hæmalum I have been able to see the nucleus clearly as well in the auxiliary cell as in the other ones of the procarp except in the carpogonium, this most probably being due to the bad preservation of the material, this having been kept in rather weak spirit. After the fertilization the auxili- ary cell increases in size, and soon two cells are cut off, one at both ends of it (Fig. 198 a). These cells again are divided into smaller ones (Fig, 198 b). Not having had sufficient mate- rial I have not been able to follow the development in detail, but the Fig. 199. Mesothamnion cari- result of the further growth is that sent. (About 120:1). of several larger and smaller round- ish bodies consisting of the nume- rous carpospores (Figs, 199 and 200). Of these bodies the two on each side are the largest; so far I have been able to follow 214 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. the evolution these originate from the two cells firstly cut off from the auxiliary cell. But besides these two larger balls several of variable size are present, these most probably originating from divisions of the cell found in the middle after the division of the auxiliary cell. Immediately after the fertilization several filaments begin to grow out from the upper end of the cell which carries the pro- carp. These filaments are branched several times and surround the cystocarp forming in this way a kind of involucrum round it (Figs. 199 and 200). Fig. 200. Mesothamnion caribaeum nov. spec. Nearly ripe cystocarp. (About 40: 1). If we now seek as to which of the other genera belonging to the Ceramiaceæ our plant is most closely related At is evident from the description and figures above that, in the vegetative formation of the thallus, it comes very near to Callithamnion. The base of the plant, the ramification of the thallus, the chromato- phores and the habit of the thallus on the whole agree perfectly well with that genus and the distribution of the tetrasporangia, too, is quite the same as that found in Callithamnion. On the other hand, with regard to the antheridial stands and especially the building of the procarp and cystocarp, it differs decidedly from that genus. As to these organs it seem.s to me that we F. Børgesen: Rhodophyceæ of the Danish W. Indies. 215 find the most closely related forms in the group of Spermothamnieæ. In this group, as in the case of our plant, the procarp is termi- nally placed and after the fertilization the cystocarp is more or less covered by fdaments in a similar way as in our plant. Judg- ing by the figure of Ptilothamnion Pluma given by Bornet ') the procarp in this plant seems to be exactly like that in the present one. In other genera, e. g. Spermothamnion we have two auxili- ary cells; but, if we consider the halfpart to the right of the schematic figure of the procarp of this genus given by Oltmanns' in Handbuch, p. 705, it is easily seen that this is exactly like the procarp in our plant. As to the antheridial stands these, too, show likeness to those found in the same group; comp., e. g., the figure 2 of Spermo- thamnion flabellatum Born, given by Bornet et Thuret, 1. c, pi. 8. Closely resembling the antheridial stands of our plant are those found in Antithamnion Plumula judging from the figure of BuFFHAM^). Much alike too, are, the antheridial stands of Compso- thamnion gracillimum as represented by the same author^). In Callithamnion, on the other hand, the antheridial stands mostly form small cushions like those I have described and figured for Callithamnion cordatum; for Callithamnion byssoides Buffham has figured (1. c, 1884, pi. X, fig. 5) the antheridial stands of this plant, these showing very great likeness to the present one, but the West Indian specimens of C. hijssoides found by me had the low, cushion-like, antheridial stands commonly found in Calli- thamnion. In Engler und Prantl, Die Natiirl. Pflanzenfamihen, I. Teil, Abt. 2 the Fam. Ceramiaceæ is divided in 15 groups; it seems to me on account of the above mentioned facts that our plant must be considered as the representative of a new group : Meso- thamnieæ forming an intermediate link between the groups Calli- thamnieæ and Spermothamnieæ. ]\|iie Vickers in her "Liste des Algues mar. de la Barbade" (Ann. sc. nat. Bot. 1905, p. 65) mentions a "Callithamnion? sp. nov. ? A des anthéridies cylindriques, comme les Pleonosporiiim, mais les sporanges ne renferment que quatre spores en tetraedres. 1) Bornet, E. et G. Thuret, Notes algologiques, p. 179, pi. 46, fig. 1. 2) Buffham, T. H., Notes on the Florideæ and on some newly-found Antheridia (Journ. Queckett Microscop. Club, vol. I, Ser. II, 1884, pi. XI, fig. 2). 3) Buffham, T. H., Notes on some Florideæ (Journ. Queckett Microscop. Club, vol. VI, ser. II,' 1896, pi. X, fig. 12—13). 216 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Je n'ai pas vu de cystocarpes". Perhaps she has had the pre- sent plant before her. The plant was dredged in deep water in a depth of about 30 meters. St. Jan: Off Annaberg. Subfam. 4. Callithamnieæ. Callithamnion Lyngb. 1. Callithamnion cordatum Børgs. Børgesen, F., Some new or little known West Indian Florideæ (Bot. Tidsskrift, vol. 30, 1909, p. 10). This plant is an epiphyte forming small, rosy, shrub-like tufts upon the host plant. It is not corticated; however, from the basal cells of the vigorous branches in the lower-most part of the thallus a single long rhizoid is often developed. It grows do\NTiwards along the wall of the large cells in the main stem (Fig. 201). These rhizoids are composed of nearly cylindrical cells about 150 fi long and 25 ft broad. The frond reaches a height from 2 — 4 cm. ; the main stem is at the bottom part nearly straight with few branches, becoming more flexuous and richly ramified higher up ; near the top the main axis disappears (Fig. 202). The base (Fig. 203 A) consists of short cells, their walls often reaching a thickness of 18 /j or more, the diameter of the whole cell measuring about 200 /i. From the cells near the base rhizoids grow down- wards and assist in fixing the plant. Higher up in the main stems the cells grow longer becoming at the same time thinner, at first twice as long as broad (long. cell. = 300^; lat. cell. = 160^), and then nearer the top 5 — 8 times as long as broad (long. cell. = 400//; lat. cell. ^= bOju). The uppermost branches are much thinner, only S/j. thick; they are often arch-shaped and bent inwardly (Fig. 204). The ramification is alternate, in the upper part subdichotomous. In my previous description I have said that hairs, as a rule, are absent; this is the case, too, in the older part of the thallus Fig. 201. Callitham- nion corda- tum Borgs. Rhizoid growing out from base of a brancli. (About 170 : 1). F. Børgesen : Rhodophyceæ of the Danish W. Indies. 217 where hairs seldom occur. On the other hand, in the young summits of the plant being in active growth I have now by a renewed examination of the plant found hairs in the ends of the filaments. The hairs are about 3 fj. broad and 150 // long. The sporangia are obovate-oblong, tetrahedrally divided (Fig. 203 C, D)\ they are sessile and occur on the uppermost and inward side of the Fig. 203. Callithamnion cordatum Borgs. A, base of a plant (25:1). B, end of filament with hair (100:1). C, part of tetrasporic plant (50:1). D, tetra- spore (150:1). E, part of antheridial plant (60 : 1). F, cell with antheridial stand (150 : 1). G, cystocarp (60 : 1). H, young procarp (150 : 1). /, older pro- carp with fully developed trichogyne (150:1). K, transverse section of a cystocarp (60 : 1). Fig. 202. Callithamnion cor- datum Borgs. Habit of a fe- male plant. (About 60 : 1). mother-cell. They are found in special individuals, but a few scattered tetrasporangia can also occur in the female plants (Fig. 204). The tetrasporangia are about 40// long and 27// broad. 218 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. The antheridial stands (Fig. 203 E, F) are found at the same places as the tetrasporangia; they consist of a system of closely placed, short branches, of which each bears 2 — 4 antheridia. The cystocarps (Figs. 202, 203 G, 204) are binate and trilo- bed heart-shaped, sometimes also more irregularly formed. The younger and smaller ones consist only of a single layer of carpo- spores (Fig. 203 K), but in the bigger cystocarps and especially in the more irregularly shaped several layers are also present. The carpogonial branch is four-celled and possesses a very long trichogyne (Fig. 203 /). The plant occurred as a com- mon epiphyte on Gracilaria Blodgetti and was found only in deeper water (about 15 fat- homs). It was collected \V\i\\ tetraspores, antheridia and cystocarps in the month of March. Occurred in many places in the sound between St. Tliomas and St. Jan: off Cruz Bay. Geogr. Distrib. : Hitherto found only in theabove mentioned locaUty. Fig. 204. Callithamnion cordatum Borgs. Branch with cystocarps and a single tetrasporangium (50:1). 2. Callitbaranion byssoides Arn. Arnott in Hooker, English Flora, vol. II, part I, 1833, p. 342 (Algæ by Harvey). Harvey, Manual, 1849, p. 178; Phycol. Brit, pi 262. Are- scHouGH, I. E., Phyceae Scandin. Marinae, 1850, p. 107, pi. V, B. Cfr. Schmitz, Fr., in Berichte d. deutsch, bot. Ges., Bd. XI, 1893, p. 280. Børge- sen, F., Some new or little known West Indian Florideæ (Bot. Tidsskr., vol. 30, 1909, p. 11). Regarding a comparison of the West Indian form with plants from other countries I refer to my remarks, 1. c. Here I shall restrict myself to give a short description only of the West In- dian plant (Fig. 205). It has a rather vigorous main stem whose cells are about 3 — 4 times as long as broad (lat. cell. = 140//); higher up the cells grow thinner and thinner, the youngest tips of the branches being only 9 — 10// thick. The branches emerge spirally from the F. Børgesen: Rhodophyceæ of the Danish W. Indies. 219 main stem ; below, the side-branches grow out to long filaments like the main stem ; higher up they are shorter ; in the uppermost part the ramification is subdichotomous. The plant is not corti- cated and hairs do not occur. The tetrasporangia are generally tetrahedrally divided, though cruciately divided ones occur too (Fig. 206 A). They are sessile, oblique-obovate or nearly roundish when ripe and 35—40 fx broad. The cystocarps are, when fully developed, irregularly lobed, binate. I have only found a few procarps ; from these it seems evident that the carpo- gonial branch is four-celled ; the carpogonium has a rather long trichogyne (Fig. 206 C). Antheridial plants had not been seen when I previously examined the plant ; these have now been found by renewed examination (Fig. 207). The antheridial stands occur in the same places as the tetraspor- angia, lining the upper (inner) side of the filaments. Often they are found only at the summit of the cells, sometimes they occupy nearly the whole upper side of these. They con- sist of a system of short branch- lets in which the uppermost cells are the antheridia. The antheridial stands in the West Indian plant differ rather much from those figured by Buffham^). In his specimens these have a single short axis while in the West Indian plant, as mentioned above, the antheridial stand is composed of several short branchlets. The tetrasporangia, cystocarps and antheridia occur in sepa- rate plants. The chromatophores are parietal and consist of shorter or 1) BuFFHAM, T. H., Notes on the Florideæ and on some newly-found Antheridia (Journ. of the Queckett Microsc. Club, vol. I, Ser. II, 1884, p. 341, pi. X, figs. 4, 5). Fig. 205. Callithamnion hyssoides Arn. Part of a tetrasporic plant. (About 60 : 1). 220 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. longer, in the young cells rather broad (Fig. 206 B), in the older cells narrower, irregularly sinuate ribbons (Fig. 206 F). Each cell i\ Fig. 206. Callithamnion byssoides Arn. A, B, branches with tetraspores (75:1), (150:1). C, carpogonial branch with trichogyne (160: 1). Z), young cystocarp (160: 1). E, older cystocarp (75:1). F, cell with chromatophore (75:1). I contains a single nucleus (Fig. 206 5), but I wish to point out that I have not succeeded in seeing the nucleus in the older and larger cells. The plant was found with cystocarps, anthe- ridia and tetrasporangia in the months of January and February. It occurred in shallow water, in a sheltered place upon the roots of the mangroves or upon other algæ growing here. St. Croix: The Lagoon of Christiansted. Geogr. Distrib.: Atlantic coast of Europe and North Africa, Mediterranean Sea, Atlantic coast of North America, West Indies etc. 3. Callithamnion spec. This plant being quite sterile (only once a speci- men was found with a few nearly ripe tetraspor- angia) I have not been able to determine it exactly, but as it was found abundantly in some places in deep water I just want to give a short des- cription of it and a few figures too (Fig. 208). Fig. 207. Callithamnion byssoides Arn. Antheridial stand. (About 350 : 1). I F. Børgesen: Rhodophyceæ of the Danish W. Indies. 221 The plant grows epiphytically upon larger algæ, e. g. Hali- meda, Udotea, Avrainvillea and forms entangled masses together with Cladophora crispula, Cladophoropsis etc. It is fastened to the host plants by means of rhizoids growing out from the cells in the main filaments, often rather high up in the plants (Fig. 208 b) ; the primary base I have not seen. The rhizoids end in small, irregularly shaped discs. The plant has no cortical layer. The cells in the main fila- ments are nearly cylin- drical about 2,5 mm. long and 400// broad. The ramification is multilateral or alter- nate, in the upper part of the thallus often secund. A few of the branches grow out as filaments like the main filaments, but most of them become shorter branchlets with definite growth ; these branch- lets are repeatedly pseudodichotomously ramified, having very long cylindrical cells often reaching a length of 3 mm. or even more, while their breadth is only about 100 fj. The few tetraspor- angia found were tetrahedrally divided. Found in a depth of about 10—12 meters. St. Thomas: In the sea to the west of Water Island where in many places it occurred in large quantities. Fig. 208. a plant. Callithamnion spec, a, upper end of b, part of a filament with rhizoids. (About 40:1). 222 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Seirospora Harvey. Seirospora occidentalis Børgs. Børgesen, F., Some new or little known West Indian Florideæ (Bot. Tidsskr. vol. 30, 1909, p. 14). This interesting plant (Fig. 209) was found among the above- mentioned Callithamnion cordaium as an epiphyte upon Gracilaria Blodgettii. Fig. 209. Seirospora occidentalis Borgs. Part of a female plant. (About 70 : 1). The plant is much ramified and forms small, dense bushes about 1—2 cm. high. The main stem is fastened to the host plant by means of short, thick-walled rhizoids emerging from the lowermost cells (Fig. 210 A). The cells found here are short, nearly as long as broad, about 200// thick having very thick walls (the wall ca. 40/^ thick). F. Borgesen: Rhodophyceæ of the Danish W. Indies. 223 Higher up in the stem the cells grow evenly, thin- ner in the middle of the plant about 85 tj. thick, becoming at the same time more thin-walled and long- er (4 — 5 times as long as broad), decreasing in thick- ness evenly towards the apex, the ultimate cells being only 8 — 11 p. thick. These often, but not always, end in a thin hair (Figs. 210 A 211^). Breadth of the hair about 3/^. The plant is not corti- cated. It is richly rami- fied on all sides, in the uppermost part subdicho- tomously. Both the younger and older cells have only a single nucleus (Fig. 210 B, F), in accor dance with the description of Schmitz^). The parietal chromato Fig. 210. Seirospora occidentalis Børgs. A, base of a plant (25 : 1). B and C, branches with tetraspores 60 : 1). D, branch with antheridia (60 : 1). E, antheridia (150 : 1). F, cells with chromatophores and nucleus (150 : 1). Fig. 211. Seirospora occidentalis Borgs. A, branch with nearly ripe cysto- carp. B, D, young cystocarps (150:1). C, procarp (150:1). ^) Schmitz, Fr., Die Gattung MicroJ/iamraton J. Ag. (= Seirospora Harv.) Ber. d. deutschen bot. Gesellsch., Bd. XI, 1893, p. 273. 224 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. phores are thread-like, shorter or longer, and irregularly sinuated (Fig. 210 B, E, F). I have found plants with tetraspores, antheridia and cysto- carps, which all occur on separate individuals. The tetraspores _^are sessile on the uppermost and inner side of the mother-cells (Fig. 210 B, C), when young they are oval or obovate, when quite developed nearly spheric- al; they are commonly tetra- hedrally divided more seldom cruciately (Fig. 210 C). The cystocarps are com- posed of two oppositely-placed gonimoblasts, which, when ripe, consist of the ramified monili- form threads of the uniseriated, nearly spherical carpospores (Figs. 209, 211 A) ; the latter are about 40 — 42 /i broad. These peculiar seirosporic cysto- carps agree very well, apart from the form and size, with those found in Seirospora Griffithsiana Harv. and which BoRNET was the first (Notes algologiques, I (1876) p. XIV) to explain as cystocarps in contradistinction to the para- spores (seirospores) also occur- ring in this plant. Fig. 211 C shows a procarp. 1 have only succeeded in find- ing remains of the trichogyne, it seems to be very short-lived as Schmitz (1. c, p. 280) also men- tions being the case in Seiro- spora interrupla (Engl. Bot.). Most probably this is the reason why BuFFHAM^) has not detected the trichogynes in plants examined by him. 1) BuFFHAM, T, H., On the reproductive organs, especially the Antheridia, of some of the Floridese. (Journal of the Queckett Microscopical Club, Vol. IV, Ser. II (1891) p. 252). Fig. 212. Seirospora occidentalis Borgs. Part of a plant with paraspores. (About 125:1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 225 I have not been able to see with certainty, in the rather scanty material, whether the carpogonial branch consists of 3 or 4 cells. Schmitz (1. c.) in his diagnosis of the genus Seirospora describes the carpogonial branch as most often 4-celled, but in Seirospora interriipta he found (1. c. p. 280, note 3) the carpogonial branch consisting of 3 cells only. After fertilization both the auxiliary cells begin to divide and produce the ramified, sporogenous fdaments of which the cystocarps consist. The antheridial stands are distributed in the same way as the tetraspores, placed on the uppermost and inward side of the mother-cell (Fig. 210 D). They consist of quite short branchlets which bear the spermatangia. Most often they grow quite closely together in dense tufts, sometimes too, as Fig. 210 E shows, more scattered. When I described this plant I had not come across the para- spores. Having now examined some more collections of algæ I have twice found plants with paraspores which I refer, without hesitation, to this species. In one of the collections (from St. Thomas, Fig. 212) the specimen with paraspores was found together with other fructiferous parts of this plant; in the other (from St. Croix) the paraspore-bearing specimen was not found in company with any other specimen of this species. The branchlets forming the paraspores occur in the same places as the tetrasporangia, viz. at the upper and inner side of the cells in the filaments. They consist of short cells filled with reserve nutriments. The cells have thick walls, and become, when ripe, nearly spherical. The diameter of the paraspores is about 18—20 (ji. This species has been found epiphytic upon Gracilaria Blod- gettii in a depth of about 15 fathoms and besides I have found a few specimens intermingled among Cladophora and Callithamnion in about the same depth. Once it was found washed ashore growing upon an old piece of Sargassum vulgare. It has been found in several places in the sound between St. Thomas and St. Jan: e. g. off Christiansfort. St. Thomas in the sea to the west of Water Island. St. Croix: near the estate Lt. Princess (washed ashore). Geogr. Distrib.: Hitherto not found in other regions. Dansk Botanisk Arkiv, Bd. 3. Nr. 1 (1917). 15 226 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Subfam. 5. Crouanieæ. Antithamnion Nagl. 1, Aniithamnion antillanum nov. spec. Fronde cæspitosa, filis repentibus decumbentibusque, sub- strato adfixis, filis erectiusculis ramulis oppositis instructis. Ramuli alterne pinnati, pinnis pinnulas singulas (raro plures) in exteriori latere gerentibus ; pinnulis plerumque ex binis-quaternis (raro pluribus) cellulis compositis, in superiori (interiori) latere glandula o vat a instructis. Tetrasporangia cruciatim divisa, e cellula basali pinnularum orta. The base of the plant consists of decumbent, creeping filaments, from which the erect filaments arise; often, too, the ends of these filaments grow upwards. The creeping filaments are fastened to the host plant by means of vigorous haptera (Fig. 213). The stalk of the hapteron is of variable length, often moniliform, the cells being oval of shape. They have thick walls; their length varies between 35 — 65/^ or more, their breadth is about 20—25/^. The stalk ends in a flat, disk, consisting of coherent rhizoids. The erect filaments Fig. 214 are oppositely and distichously ramified and bear two kind of branches: some of them growing out as main stems like themselves, the others as short branchlets with limited growth. The cells in the main stem are nearly cylindrical, of variable size from 70—200// long and about 40— 50/z broad. Fig. 213. Antithamnion antilla- jj^g branchlets (Fig.2 15) are alternat- num nov. spec. Part of a de- . -^ , xi • V • i j cumbent filament from which mgly ramified, the pmnæ bemg placed downwards rhizoids, upwards distichously along both sides of the branchlets are issued. (About 85:1). rachis. k 1 F. Børgesen: Rhodophyceæ of the Danish W. Indies. 227 The basal cells in the branchlets are small, nearly quadratic (comp. Figs. 213 and 214), while the other cells in the rachis are nearly cylindrical, a little thicker upwards where the pinnæ issue. The basal cell is very persistent, more or less immersed in the mother cell and remains after the branchlets have died; as pointed out by Howe^) for A. densiim so in the present species also, rhizoids grow out from this cell ; adventitious, erect fila- ments too arise from it. The cells in the rachis of the branchlets are from 20 — 24 fi broad and 50 — 150// long or more. The pinnæ are simple or ramified and generally provided with a single pinnule growing out mostly from the secund cell from the base on the distal side of the pinnæ (Fig. 215). These pinnules (Fig. 216 b, c, d) consist generally of two to four, seldom more, cells about 1^/2 times as long as broad (long, cell. = 10 f/, lat. 13 /i). Nearly every- one of these small pinnules carry a large, oval, clear gland-cell on their upper (inner) side. This is 20/^ long and 13/^ broad. As to the development and position of the glands the present plant seems to come near to A. cru- ciatum according to the description by Nestler"), still a few small differ- ences occur. While in the latter plant the gland-cell is in contact with 3 — 4 cells, in my plant, as a rule, it abuts on to two cells, or more seldom three cells (Fig. 216 h, c, d). Nor have I ever in my plant seen the "stab-oder leisten- förmigen Bildungen" which Nestler found in A. cruciatiim; but, of course, it must be remembered that I have not been able to examine living material. As to the development of the gland- cells I have once come across (in the very scarce material at hand) Fig. 214. Antithamnion antilla- num nov. spec. Part of a plant. (About 85 : 1). ^) Howe, M, A., The marine Algæ of Peru. (Memoirs of the Torrey Bot. Club, vol. XV, 1914, p. 151). -) Nestler, a., Die Blasenzellen von Antithamnion Plumula (Ellis) Thur. und Antithamnion cruciatum (Ag.) Näg. (Wissensch. Meeresunter- suchungen, III. Bd., 1, 1899). 15* 228 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 215. Antithaninion antillanuin nov. spec. Branchlet with gland- cells. (About 180 : 1). 1) Grunow, a., Algæ in tab. 6, flg. 3. a young state (Fig. 216 e); this seems exactly to correspond to the description and figures of Nestler. a young cell, the first beginning to the pinnule carrying the gland-cell, we find divided, by a longitudinal, somewhat curved wall, into two cells; of these the smaller one is the young gland-cell, while the larger cell afterwards by transverse walls is divided in two to four, seldom more cells. In the dried material a few tetrasporangia occurred (Fig. 216 a). These were of an oblong-cylindrical shape, about 90 n long, and 40 fx broad, with broadly rounded apex and base ; they were cruciately divided. The few tetrasporangia "in situ" I have come across were placed upon the basal cells of. the pinnæ in the corner -between this and the rachis of the branch. As to the gland-cells the present Anti- thamnion, as mentioned above, is closely related to A. cruciatum, but on the other hand it dillers essentially from this species. As to these organs my plant seems to come near, also, to Grunow's Sporacan- thiis compactus^), but otherwise it has no likeness to this plant. We may point out as the most charac- teristic features of our plant : the alternate branching of the branchlets through- out, the mostly single pinnule on the under (outer) side of the branchlets provided on its upper side with the gland-cell, and 'Raise der österr. Fregatte Novara", 1870, p. 60, Fig. 216. Antithamnium antillanum nov, spec. a, part of filament with tetrasporangia. b, c, d, pinnæ with gland-cells, e, development of gland- cell. (About 300 : 1). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 229 the large, subcylindrical tetrasporangia placed, as far as I have seen, at the base of the filament. The plant has been found as an epiphyte upon old remains of larger algæ in shallow water and in a rather sheltered place. St. Thomas: In the harbour of this island near the town Charlotte Amalie. 2. Antithamnion spec. Having had only a few sterile, small specimens of this plant at my disposal I prefer to let it remain without a specific name. The plant has decumbent, creep- ing filaments (Fig. 217), fastened to the substratum {Sargassumvulgare) by means of hap- tera; these have a short stalk consist- ing of more or less moniliform cells, ending in a small irregularly lobed disk. The cells in the stalk are about 50 /i long and 21 jj. broad. The cells in the creeping filaments are nearly cylindrical with thick walls ; they are about 40 fj. broad and lib II long. From these basal filaments the erect ones arise; the ends of these creeping filaments often being assurgent too. The erect filaments are oppositely ramified, each joint bearing two branchlets cruciately alternating with the pair below (Fig. 218). A few of these branchlets grow out as filaments like the main stem ; by far the greater part remain short with definite growth. The cells in the main stem are of variable size in the different filaments; they are nearly cylindrical, a little thicker above the place where the branchlets issue; their length varying about 100/^, their breadth about 30/^. The branchlets are alternatingly ramified. The lowest cells in the branchlets are short often nearly spherical ; the other cells Fig. 217. Antithamnion spec. Part of a decumbent filament with rhizoids and erect filaments (About 175:1). 230 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. Fig. 218. Antithamnion spec Part of an erect filament. (About 140 : 1). are cylindrical 2—3 times as long as broad. In the basal part of the branchlets the cells are about 16;/ broad, tapering gradu- ally upwards; the uppermost ones in the end of the filaments are often short, conical. The chro- matophores consist of irregularly shaped discs or short plates. At the summit of the young branchlets long, thin hairs are generally present (Fig. 218); these hairs are about 3 fj. thick and about 80 (J. long. Gland-cells did not occur in this plant. As mentioned above the plant was quite sterile, neither tetra- sporangia, nor other reproductive organs were found. This plant seems to come near to A. cruciaium, but the few specimens I have seen were desti- tute of gland-cells, had always opposite, not verticillate branchlets, these being alternately, not oppositely branched. The plant was found epiphytic upon an old specimen of Sargassum vulgare washed ashore. St. Croix: Near the estate Lt. Princess in the neighbourliood of Cliristiansted. Crouania J. Ag. 1. Crouania attenuata (Bonnem.) J. Ag. . Agardh, J., Algae mediter., 1842, p. 83; Spec. Alg. vol. II, p. 105; Epi- crisis, p. 84. Harvey, W. H., Nereis Bor.-Am., p. 226, pi. 31 D; Pliycol. Brit., pi. 106. Crouan in Ann. Sc. Nat., Bot., Sér. III, 1848, p. 375, tab. 12, figs. 24—25. Crouania bispora Crouan in Ann. Sc. Nat., Bot., Sér. III. p. 374, tab. 12, figs. 21—23. Mesogloia attenuata Ag., Systema, p. 51. (For more synonyms comp, also De Toni, Sylloge Alg., vol. IV, Flori- deæ, p. 1417). This species occurs in shallow water both in exposed and sheltered places, and in deep water ; as the specimens vary rather much according to the different growing places I shall first give a short description of a plant from an exposed locality and after- wards compare it with a specimen from deep water. F. Børgesen: Rhodophyceæ of the Danish W. Indies. 231 The specimen from an exposed place which I am going to describe was growing upon Amphiroa fragilissima originating from a coral reef at the south coast of St. Croix, The specimens found here are scarcely 1 cm, high. Their colour is more or less bluish green, while specimens from more protected places and from deep water have a red brown colour. The thallus consists of a central ramified filament composed of large cylindrical cells near the upper end of which a whirl of 4 di- or trichotomously ramified branchlets are issued (Fig. 219). The basal part of the fila- ments is decumbent and fastened to the host plant by means of rhizoids. In the most vigorously developed rhizoids the stalk is moniliform owing to the oval shape of the thickwalled cells, in the less vigorous cylindrical ; the stalk ends in short, irregularly ramified filaments often forming a small disc. These rhizoids grow out from the basal cell of the branchlets (Fig. 220). The cells in the central fila- ments are cyhndrical with thick walls ; in vigorous filaments they reach a length of about 180 // and a breadth of 120/^. They are not corticated. The branchlets are repeatedly di- or trichotomously ramified ; the cells in the branch- lets are broadest and shortest near the base, tapering gradually upwards growing at the same time longer. The uppermost ones, in any case in the lower part of the thallus, are often long cylin- drical growing up between the filaments of the branchlets above, and because of this, covering in most cases the main stem quite densely (Fig. 219). In the cells of the branchlets we find well developed chro- matophores. These consist of a parietal campanulate plate, down- wards with large openings or with irregularly shaped prolongations. In the cells of the central filaments the chromatophores, on the Fig. 219. Crouania attenuata Bonnern.) J. Ag. Part of a main filament with branchlets. (About 240:1). 232 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. other hand, are much less developed; they are here present as quite thin ribbons with a great distance between them. If we now compare these small, but robust specimens with the ones occurring in deep water, we shall find the habit of the plant much altered. The plant is much larger often 2 — 3 cm. high, but, on the other hand, much more slender and weakly developed. All parts of the plants are more or less elongated, the cells of the central filaments being longer, but less broad and having thinner walls. The same holds good with regard to the branchlets, these being, on the whole, less developed, shorter, and not form- ing such a dense cover round the axis as they did in most cases in the plants from exposed places. As to the reproductory organs I only found tetraspores and antheridia. The tetrasporangia issue from the cell in the branchlets (Fig. 221); they cruciately divided. The antheridia are developed quite in the same w-ay as described for Crouania Schousboei Thur. by Bornet and Thuret in Notes algologiques (p. 185, pi. 49, fig. 5). The peri- pheric cells of the branchlets are repeatedly dichotomously ramified, and the uppermost ones of the small cells, resulting from these divisions, are the antheridia. The plant has been found with tetraspores and antheridia in the months of Jan. — March. As mentioned above it occurs as well in shallow water as in deeper ; when growing in shallow water it is often found in rather exposed places where it is dashed constantly by the waves ; in such places it often occurs as an epiphyte upon Amphiroa fragilissima. In deep water I have only collected it once at a depth of about 20 meters ; it was here fastened to Caulerpa crassifolia. Crouania attenuata seems to be a common species along the shores of the Islands. Fig. 220. Crouania attenuata (Bonnern.) J. Ag. Rhizoid grow- ing out from the basal cell of a branchlet. (About 120:1). have basal are Fig. 221. Crouania attenu- ata (Bonnern.) J. Ag. Bases of branchlets with young tetrasporangia. (About 400:1). F. Børgesen : Rhodophyceæ of the Danish W. Indies, 233 Geogr, Distrib. : Mediterranean Sea, warmer shores of the Atlantic Ocean. Subfam. 6. Spyridieæ. 1. Spyridia filamentosa (Wulf.) Harv. Harvey, W. H., in Hooker, Brit. Flora, vol. II, 1833, p. 336; Manual Brit. Alg., 1841, p. 101 ; Phycologia Britannica, pi. 46; Nereis Bor.-Am., 1853, part II, p. 204. Agardh, J., Spec. Alg., vol. II, p. 340; Epicrisis, p. 268. Farlow, W. G., Mar. Alg. of New England, 1881, p. 140, pi. X, fig. 1 and pi. XII, fig. 2. Hauck, F., Meeresalgen, p. 115. De Toni, Sylloge Alg., vol. IV, sect. Ill, p. 1427 (ubi synomyna pluria). Fucus filamentosus Wulfen, Cryptogama aquatica in Roemer's Archiv für die Botanik, III, 1803, p. 64. Spyridia filamentosa is a very variable plant as is sufficiently clear from the many names the different forms have received in the course of time. To understand this we need only to consider the many different forms Kützing has figured in "Tabulæ phycologicæ", having put them down as separate forms (comp. De Toni, 1. c). It is, of course, always a difficult thing to decide, whether any of these forms really ought to be considered as a proper species or not. But to judge from the West Indian material the species seems to be a very plastic plant, highly influenced by the external conditions. In the West Indies I have found it in more sheltered places and in shallow water. It is common in lagoons and bays, but the mechanical influence of the waves may often he strong even in such places e. g. in certain places in the harbour of Charlotte Amalia. Light is another factor having much influence upon the shape of the plant. Of course this varies a good deal according to whether the plant is growing upon coral reef or atta- ched to the roots of mangroves, thus Fig. 222. Spyridia filamentosa growing in the shade of these trees. (^"1^/) "^J^- ^^'^ fj^^^""^' .■,.-,,. . , men from the coast of St. Croix And again whether it grows in clear near Christiansted. (About 16:1). 234 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. water upon stones lying upon the dazzling white sand bottom or in lagoons in muddy water. Often, too, it is found together with other algæ as entangled masses lying loose upon the bottom. From this it is clear that the external conditions under which this plant grows in the West Indies are very variable. The specimens found are ramified on all sides (Fig. 222). They have corticated bran- ches and branchlets. Some differences, as to the more or less rich ramification or to the shape and size of the bark-cells, may occur, but it is not here that the essential differences are to be found. It is in the case of the size and shape of the ramuli that we find the chief differences (comp, fig. 223). These may be thick, or thin. Fig. 223. Spyridia fila- in some Specimens they have a broad base mentosa (Wulf.) Harv. , . i i • 4-u 4.u a, a ramulus with long and taper evenly upwards, in others they cells froni the specimen have nearly the same breadth along their ?aTuluswi^lfshort'ceIls ^^hole length. The first mentioned end in a from the specimen figu- long attenuate spine, the last mentioned in '''^'''^T6oft).^^^''°"* a short spine. The cells in the ramuh are either cylindrical, or barrel-shaped, in some specimens nearly as long as broad, in others often more than three times as long as broad. No doubt these variations are due to the influ- ence of different external conditions. For instance specimens growing in more open places, upon coral reefs etc. in strong light have vigorous, but mostly short ramuli with short cells, while specimens from lagoons growing in the shade of the mangroves have long, thin ramuli with long cells. In some specimens I have found numerous long, thin hairs issuing from the cortical cells: these were growing in an open ^ig. 224. Spyridia fiUmentosa place with much light. (Wulf.) Harv. Part of speci- The figure (Fig. 222) shows a part SSii fC AuTsa^'sf Ja"! of a specimen from a more protected (About 16 : l). F. Børgesen: Rhodophyceæ of the Danish W. Indies. 235 place with rather long ramuli, and Fig. 224 another specimen from an open place with short, robust ramuli. Farlow points out (in "The Marine Algæ of New England", p. 140) that : "The individuals which bear the cystocarps are distinct from those which bear the antheridia. and may be recognized by their more dense habit". The single cystocarpic specimen I have come across was very like the one figured in (Fig. 222). Fig. 225 shows a bilobed cystocarp ; in the halfpart to the left the arrange- ment of the carpospores Fig. 226^ .S;>^rfV/m /?iame«