HOW TO KNOW THE FRESH-WATER ALGAE 



251a (244) Cells bearing setae with sheathed bases. See Fig. 150. 

 COLEOCHAETE 



251b Cells without setae, or if setae present, without sheathed bases. 252 



252a Endophytic in the walls of other algae. See Fig. 175 



ENTOCLADIA 



252b Not endophytic in the walls of other algae 253 



253a Some cells bearing setae. Fig. 179 CHAETOPELTIS 



Fig. 179. 

 Berth. 



Chaetopeltis orbicularis 



Figure 179 



This plant forms relatively small 

 circular discs composed of indis- 

 tinctly radiating filaments closely 

 grown together side by side. It should 

 be compared with Coleochaete (Fig. 

 156). Almost every cell in the thal- 

 lus bears a long, very slender, hair- 

 like seta. 



253b Setae lacking 254 



254a Thallus a thin expansion, 1 cell in thickness; a circular disc or 

 a somewhat irregular expansion. Fig. 180 PROTODERMA 



Fig. 180. Protoderma viride Kuetz. 



This prostrate plant forms a 

 cushion-like thallus 1 cell in thick- 

 ness at the margin and one which 

 shows very irregular branching of 

 short filaments. It is to be found 

 growing on the stems of sub- 

 merged aquatic plants. 



Figure 180 



254b Thallus cushion-like, several cells in thickness 255 



114 



