2o6 



A TEXTBOOK OF THEORETICAL BOTANY 



they are formed, they function as asexual zoospores and give rise to fresh sori in 

 the way aheady described. These zoospores are spherical bodies with a very 



■ «• 'i 



. . 





Fig. 198. — Synchytrhim taraxaci. Sorus in leaf of 

 dandelion. 



long apical flagellum. When they reach the host cell the flagellum shortens 

 and contracts until finally it is absorbed and the body enters the host tissue 

 as a naked mass. On the other hand, if as a result of lack of sufiicient moisture 



. Zoospores 



Prosorus 



Winter Sporangium 



Sorus 



\ 



Summer Sporangium 



Zygote 



'Zoospores 

 Fig. 199. — Life-cycle oi Synchytrium endobioticiim. 



the zoospores are retained within the sporangium for a longer time, they 

 appear to get smaller in size, and on liberation they then function as gametes, 

 fusing in pairs to produce biflagellate zygotes. The zygote also enters the 



