370 Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



My material was sterile. 



The only known organs of reproduction are tetraspores; these 

 have zonate division and occur immersed in the swollen ends of 

 the branchlets. 



At the islands I have dredged this plant in deep water only, 

 at depths of about 20 — 30 meters. 



St. Jan: In the sound between this island and St. Thomas in seve- 

 ral places. St. Thomas: In the sea to the west of Water Island. 

 Geogr. Distrib.: West Indies. 



V. Rhodymeniales. 



Fam. 1. Sphæroccocaceæ. 

 Subfam. 1. Ceratodictyeæ. 



Gelidiopsis Schmitz. 



1. Gelidiopsis rigida (Vahl) Weber-van Bosse. 



Weber-van Bosse, A., Note sur deux algues de I'Archipel Malaisien 

 (Recueil de travaux bot. Néerl., Vol. 1, p. 104, 1904). Okamura, K., Icones 

 of Japanese Algæ, vol. II, 1912, p. 34 and p. 188, pi. 59, figs. 1—6. 



Fucus rigidus Vahl, Beskrivelse over endeel cryptog. Planter fra St. 

 Croix (Skrivter af Naturhistorie-Selskabet, 5. Bd., 2. Hefte, Kiøbenhavn 

 1802, p. 46). 



Gelidium rigidum (Vahl) Grev., Alg. Brit., p. LVII. Kützing, Spec. 

 Alg., p. 766; J. Agardh, Spec. Alg., vol. Il, p. 468; Epicrisis, p. 548. 



Sphærococcus rigidus Ag., Spec. Alg., p. 285; Syst., p. 227. 



Fucus corneus var. spinæformis Turn., Fuci, IV, p. 149. 



Echinocaulon spinellum Ktitz., Phyc gen., p. 40; Spec, p. 762; Tab. 

 phycol., vol. 18, tab. 38. 



Echinocaulon ramelliferum Kiitz., Tab. Phycol., vol. 18, p. 14, pi. 39. 



Echinocaulon rigidum Kiitz., Tab. Phycol., vol. 18, pi. 40. 



Gelidiopsis rigida is a common alga upon coral reefs, stones, 

 shells etc. upon which its decumbent base creeps; it forms more or 

 less dense tufts upto a heigth of about 10 cm or more. It has a 

 terete thallus of a very rigid, cartilaginous consistency and is rather 



