CHYTRIDIALES 457 



smaller and receptive thallus, in the process, forming a tube which 

 penetrates the contributing thallus and through which most of the 

 contents of this thallus are discharged, germination not observed. 



So far as is known parasitic only on the fresh-water green alga 

 Draparnaldia, an inhabitant of cool, clear, running water. 



Shen (1944) identified a fungus, which he found in China on Drap- 

 arnaldia, with Sporophlyctis rostrata Serbinow and concluded that, 

 because of the presence of motile zoospores rather than aplanospores, 

 Sporophlyctis should be merged with Polyphagia. Undoubtedly, close 

 similarities exist between the two genera but there is a fundamental 

 difference in their type of sexual reproduction : in Polyphagus the zygote 

 is always formed in or near the tip of a special conjugation tube, 

 whereas in Sporophlyctis there is no such tube and the receptive struc- 

 ture, while smaller than the contributing thallus, is the thallus itself. This 

 becomes walled off in its distal, expanded portion (from the body of the 

 zoospore) and becomes converted into a resting spore. Other minor var- 

 iations are also apparent, but the aforementioned feature is sufficient 

 to separate the two genera. Shen's fungus is, therefore, here placed in 

 Sporophlyctis (p. 458) and the generic description broadened to accom- 

 modate it. 



KEY TO THE SPECIES OF SPOROPHLYCTIS 



Prosporangium apiculate; sporangium spherical, producing aplano- 

 spores S. rostrata, p. 457 



Prosporangium without an apiculus; sporangium narrowly ovate, 

 producing motile zoospores S. chinensis, p. 458 



Sporophlyctis rostrata Serbinow 



Scripta Bot. Horti Univ. Imper. Petro., 24: 163, pi. 1, figs. 13-16, pi. 2, figs. 



17-35. 1907 

 (Figs. 4 X-Y, p. 72; 29 C-E, p. 450) 



Prosporangium ovoid, with a prominent apiculus, 30-39.5 u. long by 

 9-12.7 u. in diameter, wall thin, smooth, colorless, sporangium spherical 

 or somewhat ellipsoidal, thin-walled, 23.7-3 1 .6 \i in diameter ("20.5-26.8 

 (ji x 23.7-35.5 [V [Serbinow, 1907]); rhizoids much branched, arising 

 from the main axis or also occasionally from the body of the spo- 



