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



Halimeda ihcrassata is another example. Howe divides this'&pecies 

 into several smaller ones, while I, having found intermediate 

 stages between the different forms, prefer to consider them as 

 belonging to the same species. 



It seems to me that we get a much better idea of the mutual 

 relationship of the different forms, by connecting those which 

 are obviously related, into larger species, than by dividing them 

 up in a greater number of small ones. 



This last renders it difficult to form a clear conception of 

 their mutual affinities and equally difficult to compare the geo- 

 graphical conditions of the different floras. 



Some remarks concerning the algal vegetation 



at the islands. 



In the introductory remarks to my monograph of the West 

 Indian Caiilerpas I have mentioned the external conditions under 

 which the algæ upon the whole live, and I can therefore refer 

 the reader to what I then wrote as to the nature and situation 

 of the coast and sea-bottom and to the fact that there is practi- 

 cally no tide at the islands in question. 



But, as I have not dealt with the temperature of the sea, I 

 may give here some figures which I owe to the kindness of Capt. 

 SpEERSCHNEiDErx of the Meteorological Institute, Copen- 

 hagen. 



The numbers show the mean temperature for each month 

 of the surface water in the sea at St. Thomas. 



January 25,5 July 28,3 



February 24,8 August 27,7 



March 24,9 September 27,2 1) 



April 25,6 Oktober 27,8 



May 27,2 November 27,0 



June 28,4 December 26,4 . 



I regret that I am not in a position to give much inform- 

 ation as to the algal vegetation and the associations etc. of which 

 it is composed. I had planned to go to the islands in 1915 for the 



^) For September a single observation only was made. 



