96 



PRACTICAL BOTANY. 



cell, making the Desmids very attractive objects. The 

 ability which they possess to move about adds to the fas- 

 cination of their study under the microscope. 



A great many varieties of Desmids are found. They 

 are to be looked for associated with plants growing in the 

 water and in the mud on the bottom of slow-flowing 



FIG. 55. Zygospores of Desmids. A, Euastrum pectinatum Breb., showing 

 the zygospore and the empty cell envelopes of the cells that united. ( x 400.) 

 B, Peninm margarltaceum Breb. (X 300.) C, Closterium rostratvm Ehrb., 

 early stage, showing two cells just throwing out the connecting tube through 

 which the contents of the cells will pass to unite. (X 200.) D, Desmidium 

 Swartzii Ralfs. (X 600.) (All from Bennett and Murray, after Ralfs.) 



streams, and in the shallow pools of somewhat clear water 

 in swamps and by the roadsides in spring and early sum- 

 mer. Water that is decidedly stagnant or that which 

 flows rapidly will not yield many forms. 



The Desmids multiply asexually by the formation of a 

 partition that separates the two halves of an individual 



