HOW TO KNOW THE FRESH-WATER ALGAE 



273b Branching close and entangled, often dichotomous; downward pro- 

 jecting rhizoidal branches common; cells irregularly swollen. Fig. 

 193 AEGAGROP1LA 



Fig. 193. Aegaqropila profunda (Brand) Noidst. 



This species is more irregularly branched 

 than Cladophora and has downward directed 

 rhizoidal branches. The upper filaments are 

 densely entangled and the cells are more ir- 

 regular in shape. As the species name sug- 

 gests, it is found growing on the bottom of 

 lakes at depths up to 200 feet (especially in 

 clear water). Some authorities include Aega- 

 gropila under Cladophora. 



Figure 193 



274a (270) Vegetative cells very long and cylindrical, somewhat regu- 

 larly interrupted by swollen, thick-walled cells (akinetes). See 

 Fig. 189 P1THOPHORA 



274b Akinetes lacking; cells all cylindrical or nearly so 275 



275a Branches scarce and short, or wanting altogether; if branches 



present, without repeated branching. See Fig. 158 



RHIZOCLON1UM 



275b Branches many-celled, bearing secondary branches which arise 

 irregularly so that the arbuscular habit is almost lost. See Fig. 

 192; wave-washed and winter form of CLADOPHORA 



276a (257) Setae without cross walls at the base, formed by lateral ex- 

 tensions of cells just below the anterior cross parition of the cell. 

 Fig. 194 FR1DAEA 



Fig. 194. Fridaea torrenticola Schmidle. 



This is a very rare species (the only one known 

 for the genus) but is quickly identified by the long, 

 cylindrical cells which bear thread-like extensions 

 that are given off laterally just below the anterior 

 cross wall. The filaments occur in compact tufts 

 and are usually yellowish-green in color. 



Figure 194 



276b Setae formed otherwise 277 



121 



