F. Børgesen: Rhodophyceæ of the Danish W. Indies. 



299 



thus in one branchlet the cells had at its base a length of about 

 70 /i, while higher up in the branchlets they had only half this 

 length, about 35;/. 



By and by as the branchlets grow longer they at the same 

 time become straight, the cells being lengthened in the concave side 

 in proportion to those of the convex side ; by this way of growing the 

 uppermost summit of the branchlet only is constantly hook-formed. 



The trichoblasts are 

 unilaterally developed 

 and when young they 

 curve in the same direc- 

 tion as the summit of 

 the branchlet (Fig. 298). 



Later on they are 

 straightened and assume 

 the common appearance 

 of the trichoblasts. They 

 are vigorously developed 

 and 4 — 5 times pseudo- 

 dichotomously divided. 

 Nevertheless they are 

 generally shed early, 

 leaving back clearly ob- 

 servable scars. 



It has been men- 

 tioned above that the 

 trichoblasts are seriated, but, as pointed out by Falkenberg, 

 a trichoblast is occasionally placed somewhat out of the series. 

 This is according to Falkenberg still more the case in the tetra- 

 sporic plant, but having had only sterile plants at my disposal, I 

 refer as to this matter to the description of Falkenberg. 



The plant was found in a rather exposed locality, growing 

 between and sheltered by some larger algæ. These algæ, especially 

 Caulerpa racemosa f. reducta, Cladophoropsis membranacea, Valonia 

 utricularis, Jania etc. formed upon the reef a dense carpet in 

 which smaller algæ, e. g. Polysiphonia ferulacea and the present 

 one were creeping. 



On the shores of the islands it has only been found once, at St. Tho- 

 mas: Near Charlotte Amalia on the reef connecting the Hurricane Island 

 with St. Thomas. 



Geogr. D ist rib.: Hitherto only found once in the Mediterranean 

 Sea at Naples. 



Fig. 298. Lophosiphonia cristata Falkenb. 

 Summit of branchlet. (About 180:1). 



