ALU.E 



113 



often more abundant, a single branch from the main body 

 bears several lateral oogonia and a terminal coiled anther- 

 idium (Fig. 102, B). 



The two important facts illustrated by Vaucheria are 

 the ccenocytic body and the development of special cells to 

 act as sex organs. 



FIG. 103. Spirogyra: one complete cell, showing the spiral, band-like chloroplasts, 

 with embedded pyrenoids, and a nucleus (near the center) swung by radiating 

 strands of cytoplasm. 



69. Spirogyra. 



This is one of the most 

 common of the pond 

 scums, occurring in 

 slippery and often 

 frothy masses of deli- 

 cate filaments floating 

 in still water or about 

 springs. The filaments 

 are simple, and are not 

 anchored by a special 

 basal cell. 



The cells contain re- 

 markable chloroplasts, 

 which are bands pass- 

 ing spirally about with- 

 in the cell-wall (Figs. 

 103 and 104). These 

 bands may be solitary 

 or several in a cell, and 

 form very striking and 



Fio. 104. Spirogyra: A-C, various stages in the 

 development of sexual tubes; D, a completed 

 oospore. 



