94 



PRACTICAL BOTANY. 



the cells. There is no 

 alternation of genera- 

 tions. The plant is the 

 gametophyte. The three 

 subdivisions are the 

 Desmidiece, Zygnemece, 

 and Mesocarpece. 



The Desmidieae were 

 long classed as animals. 

 There is now considered 

 to be no doubt that 

 they belong to the plant 



world. The Desmids are fresh-water plants. They are 

 microscopic in size and are of a vivid green color. They 



FIG. 52. Desmids. a, Closterium lunula 

 in the incipient stage of transverse di- 

 vision; b,Euastrumdidelta. Two cells, 

 still adherent, which have resulted from 

 the division of a single cell. Magnified. 



FIG. 53. A, Desmidium Swartzii Ralfs; B, Micrasterias rotata Grev. ; C, 

 Euastrum rostratum Ralfs; D, Cosmarium ccelatum Ralfs; E, Xanthi- 

 dium cristatum Breb.; F, Staurastrum Arachne Ralfs; G, Clo*terium 

 Dianse Ehrb. ; H, Docidium baculum Breb. (All from Bennett and 

 Murray, after Ralfs, and variously magnified.) 



