DESMIDS, DIATOMS, AND FRESH-WATER ALGJK. 81 



a. Each semi-cell divided by four deep cuts into one 



end and four side 



lobes, each side-lobe 



divided by a short- 

 er cut into two sec- 

 tions, each section 



by a still shorter 



cut divided into 



two divisions, each 



division by a yet 



shorter cut divided 



into two parts, and 



each part with two 



teeth. Desmid very large. 31. radiosa, Fig. 32. 

 a. Each semi-cell divided by four cuts into one end 



and four side lobes, each side-lobe divided by a 



shorter cut into two parts, and each part with 



two teeth. M. rotdta, Fig. 33. 



Fig. 32. Micrasterias radiosa. 



Fig. 33. Micrasterias rotata. Fig. 34. Micrasterias truncata. 



a. Each semi-cell divided by two cuts into one end 

 and two side-lobes, each side-lobe by a shorter cut 

 divided into two parts, and each part with two 



