CHYTRIDIALES 



37 



The formation of resting spores is preceded by a sexual act by which 

 a small male plant sends out an extramatrical copulation tube to a neigh- 

 boring, larger, similar female plant into which the nucleus and most of 

 the male cytoplasm migrates (Fig. 21, 6 to 8). The female plant sur- 







,.„ FlG - 20 -— Rh izidiomyces apophysatus. 1. Oogonium of Saprolegnia with sporangia in 

 different stages of development. 2. Beginning germination. 3. Beginning differentiation 

 of zoospores. ( X 360; after Zopf, 1885.) 



rounds itself with a firm membrane and becomes a hypnospore, whose 

 method of germination is unknown. 



The Entophlycteae continue the tendency of the Rhizophideae, first 

 formulated by Atkinson (1909a), to penetrate deeper into the host cell. 

 In Diplophlyctis intestina, a hemiparasite on Nitella, the zoospores, after 



. FlG " 21 -~ z WorhizidiumWillei. 1. Zoospore. 2. Young individual. 3 to 5 Evacua- 

 tion of zoosporangium. 6. Male individual and copulation process. 7. Female individual 

 8. Plasmogamy. (X 1,500; after Lowenthal, 1905.) 



they have been surrounded by a membrane, form a germ tube and an 

 intramatrical sac, called a germsphere by Zopf (1885). In contrast to 

 Rhizidiomyces, however, the zoospores transfer their whole content into 

 this bladder, whereupon the original zoospore membrane dissolves and 

 disappears (Fig. 22, 1). The germsphere puts out a rhizoid which swells 

 to an apophysis at its point of exit. While the rhizoid elongates and 

 branches, the germsphere swells to a sporangium which at maturity 



