HOW TO KNOW THE FRESH-WATER ALGAE 



330a Cells oblong to subcylindric; surface of wall with rows of depres- 

 sions. Fig. 234 CHLORALLANTUS 



Fig. 234. Chlorallantus oblongus Pascher, rep- 

 resented with portion of wall removed to 

 show chromatophores. 



The very regular rows of depressions (form- 

 ing teeth at the cell margin) help in the 

 identification of this species. The cells are 

 capsule-like in shape and are found scattered 

 about among other algae from open bogs. 

 Only 1 species has been reported from the 

 United States. 



Figure 234 



330b Cells with other shapes 331 



331a Cells oval or biconvex. Fig. 235 TRACHYCHLORON 



Fig. 235. Trachychloron biconicum Pascher. 



Cells of this genus, like Chlorallantus (Fig. 

 234), have depressions in the wall. They are 

 broadly elliptic or oval or fusiform in shape 

 and contain a gracefully curved chromato- 

 phore. But one species has been reported 

 Figure 235 from this country. 



331b Cells triangular, pyramidal, or tetragonal 332 



332a Cells pyramidal or tetragonal. Fig. 236 TETRAGONIELLA 



Fig. 236. Tetragoniella gigas 

 Pascher. a, optical section 

 showing chromatophores and 

 reticular nature of the proto- 

 plast; b, exterior of cell show- 

 ing scrobiculate wall. 



The cells in this genus are 

 beautifully sculptured by regu- 

 largly arranged rows of depres- 

 sions. According to position 

 the cells show different shapes, 

 Figure 236 triangular or tetragonal. One 



species is reported from mixtures of algae taken from open bogs. 



141 



