HOW TO KNOW THE FRESH-WATER ALGAE 



422a Cells erect, subcylindrical clubs, straight or curved; epiphytic; 

 endospores cut off successively at the tips of cylindrical proto- 

 plasts. Fig. 306 CHAMAESIPHON 



Fig. 306. Chamaesiphon incrustans Gru- 

 now. 



These club-shaped or cylindrical plants 

 grow as epiphytes on filamentous algae 

 and whereas they may be solitary they 

 usually occur in gregarious patches. When 

 mature the end of the protoplast cuts off 

 rounded-up spores, "endospores" which 

 float away as regenerative elements. 



Figure 306 



422b Cells some other shape; gregarious, forming horizontal expanses 

 or cushions 423 



423a Perforating shells, forming short irregular, spreading filaments 

 (filamentous character not clearly evident). Fig. 307 HYELLA 



Fig. 307. Hyella fontana Huber 

 & Jadin. 



Most species of this genus are 

 marine but some occur in fresh 

 water, boring into shells of mol- 

 luscs. The plant is a short, ir- 

 regularly branched filament, some- 

 times forming a cushion-like mass. 

 The substrate must be treated with dilute acetic acid to dissolve away 

 the lime before the plants can be studied satisfactorily. 



423b Not perforating shells; plant mass expanded or cushion-like . . 424 



Figure 307 



424a Plant mass composed of cells arranged in 1 layer. Fig. 308 .... 

 XENOCOCCUS 



Figure 308 



Xenococcus Schousbei Thur. 

 are at least 2 species of this 



Fig. 308 



There 



genus found in the fresh waters with- 

 in the United States, most forms be- 

 ing marine. They occur as patches of 

 blue-green cells, compactly arranged 

 as epiphytes on filamentous algae. Cells 

 form endospores although they may re- 

 produce actively by fission. 



176 



