HOW TO KNOW THE FRESH-WATER ALGAE 



409b Spores not adjacent to the heterocysts; heterocysts at both ends 

 of the trichome. Fig. 296 ANABAENOPSIS 



Fig. 296. Anabaenopsis Elenkinii Miller. 

 (Redrawn from Smith). 



There are 3 species of this genus re- 

 ported from the plankton in the United 

 States. The trichomes are usually rela- 

 tively short and are coiled. 



Figure 296 



410a (408) Thallus composed of many trichomes; usually parallel with- 

 in colonial mucilage 411 



410b Plant a solitary trichome, or if aggregated, not parallel, but en- 

 tangled within colonial mucilage 413 



411a Trichomes inclosed in abundant mucilage; arranged to form a 

 hollow, attached tubular thallus. Fig. 297 WOLLEA 



Fig. 297. Wollea saccata (Wolle) Born. & Flah. a, habit 

 of colony; b, trichomes in detail showing heterocysts, 

 and akinetes in a series. 



The filaments of this species He more or less parallel 

 in long, gelatinous, tube-like or sac-like thalli which grow 

 vertically from the bottom in standing water. The cells 

 are barrel-shaped or Anabaena-like, and the intercalary 

 heterocysts are cylindrical or nearly so. 



Figure 297 



411b Thallus not a gelatinous tube 412 



171 



