70 THE FUNGI WHICH CAUSE PLANT DISEASE 



spore. (Fig. 42.) After a more or less protracted period of rest 

 this produces zoospores. 



The family includes some fifty species, all of which, except two 

 small genera, are parasitic upon land plants. 



Key to Genera of Synchytriacese 



Zoosporangia formed by direct division of 



the entire plasma of the young fruiting 



body. 



Swarm sporangia completely filling the 



host cell, membrane united to the 



wall of the host cell I. Rozella. 



Swarm sporangia lying free in the host cell 



Parasitic on alg£e 2. Woronina. 



Parasitic on land plants 3. Woroniella. 



Zoosporangia formed by division of an ini- 

 tial cell to forma sorus of sporangial cells. 

 Sporangia formed directly from the full- 

 grown plant body 4. Synchytrium, p. 70. 



Sporangia formed by the division of a thin- 

 walled mother cell after its escape 

 from the plant body 5. Pycnochytrium, p. 72. 



Synchytrium de Bary & Woronin 

 Upon reaching maturity the plant body develops directly into 

 a sporangial sorus. Both zoosporangia and winter spores present. 



Fig. 41. — Showing nucleus in Synchytrium. After Stevens. 



S. endobioticum (Schilb.) Perc, the cause of a very serious wart 

 disease of the potato, was originally described as Chrysophlyctis 

 endobioticum by Schilberszky ^^ and transferred to Synchytrivun 

 by Percival." It invaded America about 1909."^ It was reported 

 from Africa by Zimmermann.'^ 



