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



311 



come polysiphonous (cfr. Falkenberg, pi. 13, fig. 14). In the tetra- 

 sporic plant, on the other hand, the upper end of the main stem in 

 the trichoblast becomes polysiphonous and transformed into stichi- 

 dia, while the lowest part remains monosiphonous (Fig. 317 a). 



The polysiphonous side-or- 

 gans are developed quite inde- 

 pendently of the trichoblasts. As 

 pointed out by Falkenberg 

 they are of later origin than 

 the trichoblast, first appearing 

 after the division of the seg- 

 ments in the main filament 

 and must be considered as ad- 

 ventitious branches. Falken- 

 berg found them rather regu- 

 larly distributed , generally 

 placed with ^4 divergency a 

 single one upon each segment. 

 In my plants the arrangement 

 was not so regular, as segments 

 without branches often occur- 

 red. As indicated by Falken- 

 berg the central axis of these 

 reaches into the central cell in 

 the main filament (Fig. 316); 

 this, I think, largely supports 

 the supposition that they really 

 are of endogenous origin. The 

 greatest part of these branches 

 remains short, and spinelike ; now 

 and then a single one gets a 

 continuous growi-h like the main 

 filament and contributes to the 

 ramification of the plant. The spinelike branchlets are of a rather 

 soft consistence ; they are always undivided and consist of up to 

 ten segments with four pericentral cells, the segments getting smaller 

 and smaller towards the top. In the uppermost segment only a single 

 cell is present. 



From the basal pericentral cell of these branchlets hyphæ-like 



Fig. 314. Wrightiella Tumanowiczii 

 (Gatty) Schmitz. Part of a main axis 

 with trichoblasts and spinelike branch- 

 lets. From the basal cells of these hy- 

 phæ are seen growing downwards for- 

 ming the cortical layer. 

 'About 6U:1). 



