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 

 Mciliate. 

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

 Green Alga?, found in felt-like masses of coarse filaments in 

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



Fig. 9. Vaucheria geminafa, a Siphon form, showing a portion of the ccenocytic 

 body (.4) 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 (/>) it is 

 discharged later as a large multiciliate 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- 

 4 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- 



