488 AQUATIC PHYCOMYCETES 



SUBFAM. CHYTRIDIOIDEAE 



Sporangium epibiotic, sessile, or occasionally interbiotic; rhizoids 

 entirely endobiotic or with the tips in the substratum, delicate, tapering; 

 resting spore endo-, epi-, or interbiotic, sexually or asexually formed. 



CHYTRIDIUM Braun 



Betrachtungen iiber die Erscheinung der Verjiingung in der Natur. . ., p. 198. 

 Leipzig, 1851 ; Monatsber. Berlin Akad., 1855: 378 



(Fig. 31 A-Q, p. 496) 



Thallus epi- and endobiotic, monocentric, eucarpic, the epibiotic part 

 forming the rudiment of the sporangium, the endobiotic part producing 

 the vegetative system and resting spore; sporangium epibiotic, sessile, 

 operculate, formed from all or part of the enlarged body of the encysted 

 zoospore; zoospores posteriorly uniflagellate, usually with a single 

 globule; rhizoidal system endobiotic, variable in character, arising either 

 from the endobiotic tip of the germ tube or a prolongation of it or from 

 an endobiotic subsporangial apophysis; resting spore endobiotic, thick- 

 walled, often borne on a rhizoidal system, sexually or asexually formed, 

 upon germination producing an epibiotic operculate zoosporangium. 



Primarily parasites and saprophytes of fresh-water and marine algae. 



Braun's subgeneric term Euchytridium has been used occasionally in 

 a generic sense, notably by Sorokin (1883). 



As understood here, Chytridium includes all monocentric, eucarpic 

 chytrids, with or without a simple apophysis, which form an epibiotic 

 sporangium, discharge their spores after the dehiscence of a single 

 operculum, and have endobiotic resting spores. The nature of the 

 rhizoidal system produced by different species of the genus is extremely 

 variable and ranges from a delicate apparently unbranched needle-like 

 tube in C. lagenula to the broad often apophysate tubular structure 

 divided distally into tenuous branched rhizoids found in C. olla. An 

 exception to the endobiotic nature of the rhizoid is found in C. curvatum, 

 where the tip of the short subsporangial stalk evidently does not pene- 

 trate beyond the thin layer of gelatinous material surrounding the 

 Stigeoclonium filament. 



Segregation from Chytridium of the species with an unbranched 



