27 



363 



.■¥j> 



■^. 



found it in about ' -■ meter of water growing among oilier algæ. In the last-men- 

 tioned locality, somewhat far out to sea in the open bay between the last westerly 

 part of the long coral reef which stretches along the south coast of St. Croix and 

 the land I have found it growing on Halimeda-graxeh in about 10 meters depth. 

 But its real home is partly the well-sheltered places, especially the lagoons, partly 

 deeper water. In the first mentioned places it grows very commonly in 1 — 2 feet 

 of water, creeping on the soft bottom with its nearly thread-like rhizome; a few 

 times I have also found it growing even on the roots of the mangroves. 

 In deep water, where it also finds a quiet growing place, I have as 

 mentioned taken it down to a depth of about 30 meters. 



While SvEDEMUs only exceptionally found a periodical growth in 

 his material from Ceylon, this is very clearly present in the specimens 

 from shallow water in the lagoons (Fig. 7). On the other hand I have 

 not seen such a rhythmical growth in the individuals from deep 

 water (Fig. 8), where the conditions of life naturally are considerably 

 more uniform than in the lagoon with its shallow water, which is 

 very easily heated by the sun and is also more or less brackish owing 

 to the heavy rains. 



Two forms can be distinguished of this species. 



Forma typica (Weber van Bosse 1. c. p. 290) is recognizable from 

 having the pinnules nearly linear and not narrowed at the base. 



Forma mexicana distinguished by having the pinnules a little 

 narrowed at the base and broader at the apices. The sinus between 

 the pinnules is roundish. 



The two forms are very nearly related and intermediate forms 

 occur very often. 



Forma mexicana is the most common form on the shores of the 

 Danish West Indies and occurs in sheltered localities everywhere. In 

 deeper water I have got it at St. Croix in White Bay in a depth of 

 about 10 meters, at St. Thomas in the sea west of Water Island in 

 about 20—30 meters and at St. Jan off Christiansfort and America 

 Hill in the same depth. 



Forma typica 1 have only found in the sea west of Water Island 

 in about 30 meters of water. 



Geogr. D ist rib. The West Indies, Florida, Guyana, Bermudas, 

 Canary Islands etc.. Red Sea, Indian Sea, Friendly Islands etc. 



:m 



Fig. 8. 

 Caulerpa 

 crassifolia 

 (Ag.) J. Ag. 

 In deep 

 water off 

 Christians- 

 fort (St. Jan). 

 (About 1 : 1.) 



5. Caulerpa taxifolia (Vahl) Ag. 



C Ag.ardh, Spec Alg. p 435. 

 Weber van Bosse, Monographie p. 292. 



Fucus taxifolius Vahl, Skrivter af Naturhistorie-Selskabet, t. V, 2(lel Hefte, KS02, p. ;i(î. 



47- 



