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 



