26 



PLANT STRUCTURES 



in rivers and lakes (Fig. 8). The cells are long and densely 

 crowded with chloroplasts ; and in certain cells at the tips 

 of branches large numbers of zoospores are formed, which 

 have two cilia at the pointed end, and hence are said to be 

 Mediate. 



25. Vaucheria. — This is one of the most common of the 

 Green Algae, found in felt-like masses of coarse filaments in 

 shallow water and on muddy banks, and often called " green 



J2_ 



Fig. 9. Vaticheria (jeminafa, a Siphon form, showing a portion of the ccenocytic 

 body (^1) which has sent out a branch at the tip of which a sporangium (B) 

 formed, within which a large zoospore was organized, and from which (D) it is 

 discharged later as a large mitlticiliate body (C), which then begins the develop- 

 ment of a new ccenocytic body (E).— Caldwell. 



felt." The filament is very long, and usually branches ex- 

 tensively, but its great peculiarity is that there is no parti- 

 tion wall in the whole body, which forms one long continuous 

 cavity (Figs. 9, 11). This is sometimes spoken of as a one- 

 celled body, but it is a mistake. Imbedded in the exten- 

 sive cytoplasm mass, which fills the whole cavity, there are 

 not only very numerous chloroplasts, but also numerous 

 nuclei. As has been said, a single nucleus with some cyto- 



