F. Borgesen: List of species. 



447 



more or less coherent disc. The cells in the basal filaments are 

 about 5 n broad and 8 u long. 



From nearly all the cells of these filaments erect ones arise. 

 These are ramified from rather neai the base; the branches are 

 given off in all directions, but very irregularly, often several above 

 each other at the same side. And the distance between the bran- 

 ches, too, is very vari- 

 able; in some cases a row 

 of cells of the main fil- 

 aments carry a branch, 

 in other several bare cells 

 are present between those 

 bearing branches (Fig. 

 416 b). The branches are 

 straight and given off at 

 acute angles. The main 

 filaments are at the base 

 about 5 n thick and the 

 cells 12 /i long; upwards 

 they taper slowly to 

 about 2,5;/. The branches 

 are proportionally smal- 

 ler, 3 — Aifi at their base, 

 about 2 n at their sum- 

 mit. 



The sporangia are 

 linear-oblong, 11 — 12 fx 

 long and about 6 n broad. 

 They occur upon short 

 branchlets at the base 

 of the branches (Fig. 416 

 b, c). The sporangia are mostly pedicellate, rarely sessile. In the 

 upper end of the main filaments these, too, carry branchlets with 

 sporangia. 



The chromatophore is an irregularly lobed or perforated, 

 parietal plate, covering most of the cell and including a lateral 

 pyrenoid. 



The most important differences between this species and 

 Acr. gracile are, that in Acr. gracile the erect filaments are very 



Fig. 416. Acrochsetium cæspitiforme nov. spec. 



a, basal part of the plant, b, upper part of 



a filament, c, branchlet with sporangia. 



(a, about 200:1; b, about 260:1; 



c, about 600:1). 



