HOW TO KNOW THE FRESH-WATER ALGAE 



227a Filaments prostrate, creeping on larger filamentous algae. Fig. 

 161 APHANOCHAETE 



Fig. 161. Aphanochae- 

 te repens A. Br. 



There are 3 species 



of this genus w,hich 



are very common but 



are often overlooked 



because of their small 



size and their habit of 



creeping on the walls 



of larger filamentous 



algae. The simple setae, with their swollen bases extending from the 



cell wall are helpful in making identification. A. polychaete (Hansg.) 



Fritsch is characterized by having several setae on each cell. 



Figure 161 



227b Filaments not creeping on algae; floating or if prostrate, with 

 cells in discontinuous series .... 228 



228a Filaments very short (up to 20 cells); often in interrupted series. 

 229 



228b Filaments longer, in continuous series 



230 



229a Chloroplast a parietal plate extended over but a small pari of 

 the wall; usually subaerial. Fig. 162 STICHOCOCCUS 



®S3S)CZ3 



Figure 162 



Fig. 162. Stichococcus ba- 

 cillaris Naeg. 

 The difference between 

 Stichococcus and the 

 small filaments charac- 

 teristic of Hormidium (Fig. 

 168) is difficult to define. In the former genus the filaments are usually 

 relatively short (10 to 40 cells) and have a tendency to break into 

 short segments intermittently. Of the 6 species which occur in the 

 United States most are found on the bark of trees, old boards, or on 

 damp soil. The species illustrated is the most common, often occurring 

 with Protococcus on the moist bark of trees, the short filaments twisted 

 and contorted, or coiled hi one plane. 



104 



