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



267 



The erect filaments vary much 

 as to their thickness and the length 

 of the segments. Generally the fil- 

 aments are about 90 p. broad and 

 the length of the cells is about 

 140 /i, but thinner as well as thicker 

 specimens occur. This varying de- 

 velopment of the filaments is due 

 to their different ages, as new ad- 



Fig. 261. Polysiphonia havanensis Mont. 

 a. upper end of a filament with trichoblast 

 and branches; 6, part of a filament with 

 trichoblast and branch placed at the katho- 

 dic side of the trichoblast. (a, about 270:1, 

 b, about 360:1). 



Fig. 260, Polysiphonia hava- 

 nensis Mont. Part of a filament 

 with rhizoids and adventitious 

 branch. (About 50:1). 



ventitious branches are 

 formed continually (Fig. 

 260). So far as I have 

 seen, these young fila- 

 ments always seem to be 

 connected with the basal 

 cell of the former tricho- 

 blast, or with remains 

 of it. 



The trichoblasts are 

 mostly well developed, a 

 single one emerging with 

 a 7^ divergency from, each 

 segment (Fig. 259). They 

 generally cover quite 

 densely the top of the 

 filaments, and are found 

 rather far down upon 

 them. 



Most of the speci- 

 mens are quite sterile; 

 a few specimens only 

 with tetrasporangia are 



