CHYTRIDIALES 



43 



central sac which is the original strengthened zoospore. In this condi- 

 tion, the plant looks like a young heliozoan (Fig. 26, 2). On the other 

 hand, if the zoospore germinates in contact with a Eugle?ia, the sac is 

 sessile and the plant looks like a Rhizidium or a Chytridium. Later 

 the rhizoids branch greatly and can infect as many as 50 Euglenae. The 



mm fm 





m 



mmm 



m 



Fig. 27. — Polyphagus Euglenae. 1. Young zygote with both nuclei. The male nucleus 

 is still the smaller. 2 to 7. Germination of zygote with a zoosporangium. 8. Empty 

 zoosporangium. (X 670; after Wager, 1913.) 



thallus always remains unicellular and uninucleate, but in course of 

 time its membrane becomes very firm. 



At maturity, on the central sac there appears a spherical outgrowth 

 which increases at about 50/c per hour and develops into a sac about 275/* 

 long. It takes up the whole contents of the mother cell from which it is 

 abjointed. During the vegetative period the original zoospore nucleus 

 has reached dimensions similar to those of Synchytrium; it divides 

 repeatedly until several hundred daughter nuclei may be formed. The 



