276 



we find it quite destitute of trichoblasts 

 (comp. Fig. 272); it is straight and its 

 diameter increases rather quickly down- 

 wards from the small apical cell, which 

 is constantly divided by horizontal walls. 

 Up wards the filaments are rather richly 

 ramified on all sides. The branches issue 

 without any connection with the tricho- 

 blasts (Fig. 274). The distance between the 

 trichoblasts or branches varies consider- 

 ably, sometimes these issue from each 

 joint, sometimes 1 3 segments are bare. 

 The trichoblasts are richly developed 

 in some specimens, more sparingly or not 

 at all in others. 



The tetrasporangia (Fig. 275 b) are 

 found in long rows at the ends of the 

 filaments. These are mostly undivided, 

 sometimes forked. The segments con- 

 taining the tetrasporangia are spherically 

 swollen, about 80^ broad. 

 The antheridial stands of the Potysiphonias are, as is well 

 known, formed by the trichoblasts, and with regard to these or- 

 gans the present Polysiphonia belongs to the group of species 

 (e. g. atrorubescens, fastigiata, scopulorum 

 etc.)*) in which the whole trichoblast is trans- 

 formed, not having even a sterile end, as is for 

 example the case in Polysiphonia urceolata**). 

 They (Fig 275 a) are cylindrical in shape, 

 with an obtuse apex, about 400500 n 

 long and 100110 ^ broad. The pedicel 

 bearing the antheridial stand consists of 

 two cells, the short basal cell always found 

 in the trichoblasts, and a longer cylindrical 

 one. 



The cystocarps originate from the second 

 of the trichoblast, as is commonly the 



Fig. 275. Polysiphonia ma- 

 crocarpa Harv. a, filament 

 with antheridial stand; b, 

 upper end of tetrasporic 

 filament (a, about 360:1; 

 b, about 50:1). 



Fig. 276. Polysiphonia 



macrocarpa Harv. A 



nearly ripe cystocarp. 



(About 70:1). 



*) Cfr. THURET et BORNET, Etudes phycologiques, p. 86. 



'*) Gfr. ROSENVINGE, L. KOLDERUP, Sur les organes piliformes des Rho- 



domelacees (Overs, k. danske Vidensk. Selsk. Forhandl. 1903, p. 450, 



fig. 2). 



