242 



PLANT STUDIES 



in rivers and lakes (Fig. 207). The cells are long and 

 densely crowded with cliloroplasts ; and in certain cells at 

 the tips of branches large numbers of zoospores are formed, 

 which have two cilia at the jjointcd end, and hence are said 

 to be bicilidle. 



16(i. Vaucheria. — This is one of the most common of the 

 Green Alga3, found in felt-like masses of coarse filaments in 

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



, ^IIS. Vai/rhi na firitniufla. a Ri|)lion foi-in, slnnviTit; a jinrtiriTl of thr ((viiorytic 

 IkkIj' 1.1) wliicli lias scat, iiiit a liraiicli at the tip (if wliicll a s|«iraligiuin (ij) 

 fornu'd, witliin which a lari^a^ z<iosp()re was (nn;aaizr(l. and from wltii'h (7vt it is 

 (]iscliar<;ed later as a lar^a- innltirilialc tiody ( C), ^vllieh then bej,nns the develop- 

 ment of a new ctenocytic Ijody ( A" ). — ( 'A7.dwi-:i,l. 



felt." The fihiment is very long, tind usutilly branches ex- 

 tensively, but its great peculiarity is tliat there is no ptirti- 

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

 ctivity (Fig. -.'OS). 'I'his is sometimes sjxiken of as ;i oue- 

 celled body, but it is a mistake. Inil)cddcd in the exten- 

 sive cytoplasm nuiss, which fills the wluile cavity, there are 

 nut oidy very numerous chloro])lasts, luit tdso numerous 

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



