VAUCHERIA 



199 



suppressed in Vaucheria, so that the entire mass of protoplasm 

 remains together as a many-nucleate and many-ciliate unit, 

 which is really a protoplast or cell in spite of its complicated 

 structure. Some authors have regarded this zoospore as a com- 

 pound structure, that is, a mass of small, two-ciliate zoospores, 



FIG. 190. Sexual reproduction of the green felt (Vaucheria) 



A, Vaucheria sessilis ; o, oogonium; a, antheridium ; os, the thick-walled oospore, 

 and beside it an empty antheridium ; B, Vaucheria geminata, a short lateral 

 branch developing a cluster of oogonia and a later stage with mature oogonia 

 o and empty antheridium a; C, sperms; D, germinating oospore. C, after 

 Woronin; D, after Sachs 



but it is more correct to consider it a large, undivided, many- 

 nucleate protoplast. 



The sexual organs of Vaucheria are oogonia and antheridia, 

 sometimes found side by side, as in Vaucheria sessilis (Fig. 

 190, A), and sometimes in groups on special side branches, as in 

 Vaucheria geminata (Fig. 190, J5). The oogonium is a large 

 oval cell separated from the parent filament by a wall, and each 

 develops a single egg (Fig. 190, A, B, o). The young oogonium 

 contains numerous nuclei, but all of these degenerate except 

 one, which lies near the center of the cell and becomes the 

 single nucleus of the egg. The antheridium is a cell formed 



