CHYTRIDIALES 397 



length, 10-30 \x in diameter, wall somewhat thick, smooth, colorless; 

 rhizoids extensive, branched, arising from main axes generally formed 

 at the extremities of the sporangial rudiment; zoospores somewhat ovoid 

 or spherical, 4-5 \x in diameter, with a colorless eccentric globule and a 

 long flagellum, escaping successively through one or more short dis- 

 charge tubes which penetrate the wall of the alga but do not extend 

 beyond it; resting spores (?) spherical or elongated, thick- walled, 12-25 

 u, in diameter, several formed on the same thallus and connected to it 

 by one or more rhizoids, the bases of which persist as spiny or blunt 

 protuberances after the spore is free from the thallus, germination not 

 observed. 



Parasitic on Docidium ehrenbergii, Dangeard (be. cit.), France; 

 Docidium sp., Couch (1935c: 293, pi. 62, figs. 1-12), United States. 



Couch noted that the thallus varies from a short unbranched structure 

 to a long branched twisted body that may extend throughout the entire 

 length of the desmid cell (660 \l). More than one thallus may be formed 

 in a single host cell. Couch believed that the fungus was closely allied 

 to the polycentric Catenaria. It appears, however, to be an Entophlyctis- 

 like organism with a tubular reproductive rudiment. 



RHIZOS1PHON Scherffel 



Arch. Protistenk., 54: 189. 1926 

 (Figs. 24 D, p. 396; 11 K-M, p. 110) 



Thallus endobiotic, monocentric, eucarpic, polyphagous, consisting 

 of a central structure at the tip of the penetration tube of the zoospore— 

 the rudiment of the prosporangium — from which may emerge two 

 broad isodiametric unbranched hypha-like vegetative structures on 

 opposite sides (occasionally one or sometimes lacking); sporangium 

 inoperculate, partly or wholly extramatrical, formed as an outgrowth 

 of the prosporangium ; zoospores posteriorly uniflagellate, with one or 

 more globules, fully formed in the sporangium, escaping through a 

 short discharge tube ; resting spore thick-walled, with one or many glob- 

 ules, endobiotic, with or without a vegetative system, asexually or (?) 

 sexually formed, upon germination functioning as a prosporangium. 



Parasites of blue-green algae. 



