7 343 



about the ecology of the algæ on the whole and also about the conditions under 

 which the Caulerpas live in the West Indies. I shall here only point out some of 

 the papers (several of them for the rest also mentioned by Svedelius), where we 

 find information as to the occurrence of the Caulerpas, sufficient in anj' case to 

 show that these algæ do not at all live under quite uniform external conditions. 

 In the works of Harvey (15, 16), for example, we find under several species 

 indications of the mode of living of the species. The same must be said about 

 the paper of Maze and Schramm (22) where we find under every species of Caulerpa 

 even fairly detailed indications concerning the occurrence of the species, e. g. in 

 what substratum it is found, if it was growing in sheltered or exposed localities, 

 in what depth it occurred (a single species has been dredged in 50 meters depth), 

 if the water was clear or not etc. And as to the ecology of Caulerpa proliféra this 

 species has been treated so many times in different papers of different authors 

 that it must be said to be well-known. 



We have information from recent years also, e. g. in Reinbold's paper (26) 

 on the algæ collected by Johs. Schmidt in Siam; in Mile. Vickers' papers (36, 37) 

 on the algæ from the Canary Islands and from Barbadoes, in Collins' paper on 

 the algæ of Jamaica and in several others. 



The rhizome and root of the Caulerpas and their variations 

 under different external conditions. 



In my preliminary notice on the algal vegetation of the Danish West Indies 

 (5) I have pointed out that we find algæ and among them Caulerpas on rocky and 

 coral bottom, on loose bottom, gravel sand and mud bottom and finally on the 

 mangrove roots. That algæ are found on rocks etc. is very natural; most algæ at 

 least in the northern seas being, as is well known, lithophile; epiphj'tic algæ are 

 also what we should expect. On the other hand sand and mud loving algæ are 

 very peculiar the first time one sees them '). 



') I may here reprint what I have said earlier about this matter. On page 52 in my preliminary 

 paper I write the following: "Here on this loose sandbottom a rich alga- vegetation is growing, not 

 rich in species, it is true, but on the other hand rich in individuals. We here ßnd a group of algæ 

 which are adapted to establishing themselves and growing on the loose bottom (psammophile and 

 pelophile algæ) to which we have no counterpart in the northern seas. To be sure, the localities where 

 these algæ grow are rather protected against the open sea by the coralreefs or by being situated in 

 baj's, and we therefore can not compare them with the sandy, sterile west coast of Jutland f. i. where 

 the sandy bottom during gales is in a motion so lively, that even in a tropical climate we could not 

 expect to find any vegetation at all; but even in more protected localities with sandy or muddy bottom 

 in the North, fixed algae (the Characeœ excepted), as is well known, are entirelj' wanting, they occur 

 at once, however, where a stone or some other firm object is found, to which they can attach them- 

 selves. This alga-vegetation established and growing in the loose bottom is peculiar for the warmer 

 seas". I have further pointed out that the algæ we find here can be divided into two groups: The 

 creeping algæ and the algæ fixed to the same spot. The last mentioned comprehend species of Udotea, 

 Penicillus and Halimeda and have therefore no interest for us here whereas on the other hand the 

 first group comprise the CauZerpa-species. 



