F. Borgesen: Rhodophyceæ of the Danish W. Indies. 291 



ing at first the difTerent ramification of the two plants out 

 of consideration, he points out that according to the diagnosis 

 of the two species the following two differences are the only 

 found, namely: 1, the short segments of Herposiphonia seciinda 

 and 2, the lesser number of the segments and sporangia in the 

 branchlets of H. seciinda. As to the first mentioned difference he 

 remarks that this is of no great importance, as he has found in 

 all other respects a quite typical form of tenella having altogether 

 the same habitus as that of H. secunda*). And regarding the other 

 point I need only refer to my remarks above concerning the 

 small number of segments and of tetrasporangia developed in my 

 specimens. But when Falkenberg nevertheless regards the two 

 plants as separate species, he bases this upon the most essential 

 difTerence between them, viz.: the heterogeneous arrangement of 

 branches and branchlets, pointing out that he has never found 

 the ramification of H. tenella in typical specimens of H. secunda. 

 But as to this point it cannot be denied that the above descri- 

 bed specimens, actually having the ramification of both plants, 

 greatly weakens the supposition that the two plants are to be 

 regarded as two distinct species. Most probably, therefore, H. 

 secunda is nothing more than a reduced form or variety of H. tenella. 



Curiously enough, the plant coming near to secunda was found 

 intermingled with a quite normally branched var. typica of Her- 

 posiphonia tenella the contrast between the two forms being en- 

 hanced by the fact that it was provided with slender, long seg- 

 ments, much longer than those found in the form from St. Croix ; 

 for instance in one specimen the segments of the main stem were 

 100// broad and 280// long, and in the branchlets about 50// long 

 and 30// broad. 



Falkenberg too states (1. c, p. 308) that he found "beide 

 Arten in Neapel das ganze Jahr hindurch an den gleichen Stand- 

 orten neben einander". This seems to show that the two plants 

 in question are in all cases in reality more or less strongly dif- 

 ferentiated forms, and are not developed by the influence of 

 different external conditions. 



*) In this connection I also want to refer to the form which Askenasy 

 in "Forschungsreise S. M. Gazelle". IV Theil, Botanik, p. 50, pi. X, figs. 

 14 — 17 has described and figured as Polysiphonia Calothrix. From this it 

 seems to me beyond all doubt that the plant in question is our plant 

 of which Askenasy has found not only the typical tenella but also 

 secunda. According to the figures both forms have short segments. 



19* 



