CHYTRIDIALES 



41 



the sporangial sac changes into a thick-walled hypnospore whose 

 germination is not yet known. 



Because of the type of its germination, Saccomyces Da?igeardii (Serbi- 

 nov, 1907), which in Russia is parasitic on resting Euglena, is assigned 

 to the polyphagic genera. Its thallus consists of a slightly developed, 

 pyriform, extramatrical portion, a strengthened swarmspore body and a 

 much-branched intramatrical rhizoid tuft (Fig. 24, 3). At the formation 

 of the zoospores, the content of the extramatrical part passes out into a 

 pyriform sac where, inside the membrane, it breaks up into zoospores 

 (Fig. 24, 4), which in turn are freed by degeneration of the sac wall. 

 Hypnospores are formed asexually instead of sporangia. 



Fig. 25. — Sporophlyctis rostrata. 1. Infected filaments of Draparnaldia glomerata. 

 2. Young individual. 3. Mature individual. 4 to 6. Akinete formation. 7 to 9. Copu- 

 lation. (X 400; after Serbinov, 1907.) 



In the following species an extramatrical development of the thallus 

 becomes prominent, so that the single individuals simultaneously pene- 

 trate several plants of gregarious hosts, as in Bhizophlyctis Braunii 

 which is parasitic or saprophytic on diatoms and desmids. 



A similar species is Sporophlyctis rostrata (Serbinov, 1907) whose 

 thallus is extramatrical except for the last fine filaments which penetrate 

 the host cell (Fig. 25, 1). The saccate portion of the strengthened 

 zoospore is originally uninucleate, but becomes multinucleate by repeated 

 nuclear divisions. At maturity, the whole content passes out into a sac 

 (Fig. 25, 4) and there breaks up into uninucleate, non-motile akinetes 

 which are liberated by the rupture of the membrane (Fig. 25, 6). Copu- 

 lation precedes the formation of hypnospores. Two individuals fuse, 

 the content of the male passing over into the female (Fig. 25, 7 

 to 9). The wall of the hypnospore consists of two layers. Otherwise 

 its development is unknown. 



