CHYTRIDIALES 547 



broad by 2-3 \x high apophysis from which two to four main rhizoidal 

 axes arise laterally and become distally divided into numerous delicate 

 branches the tips of which penetrate the substratum; zoospores ten to 

 thirty, spherical, 3.5-4.5 \i in diameter, with an eccentric globule and 

 posterior flagellum, completing maturation and initiating motility in a 

 vesicle formed at the discharge pore upon the dehiscence of a subapical 

 operculum; resting spore not observed. 



On dead cells of Ceratium hirundinella, Peridinium sp., from Winder- 

 mere, Ingold (loc. cit.), P. cinctum, C. hirundinella, Canter (1951: 151; 

 1953: 294), Great Britain; Ceratium hirundinella, Canter (1951: 153), 

 Denmark; Ceratium hirundinella, Canter (loc. cit.), Sweden; Ceratium 

 hirundinella, Canter (loc. cit.), Italy; Ceratium hirundinella, Paterson 

 (comm.), United States. 



Paterson (loc. cit.) has recently made a limno-mycological study of 

 this species. Among other things, he determined that not only is water 

 temperature a limiting factor but also total alkalinity. The maximum 

 numbers of the fungus occurred between 19-21.5 degrees C. and within 

 an alkalinity range of 98-105.5 parts per million. 



ZYGORHIZIDIUM Lowenthal 



Arch. Protistenk., 5:228. 1905 

 (Figs. 4 P-Q, p. 72; 11 A-G, p. 110; 31 R, p. 496) 

 Ectochytrkliitm Scherffel, Arch. Protistenk., 53: 7. 1925. 



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

 forming either the rudiment of the sporangium or a receptive or con- 

 tributing thallus; sporangium operculate, epibiotic, sessile, predomi- 

 nantly formed from the enlarged body of the encysted zoospore; zoo- 

 spores posteriorly uniflagellate; rhizoidal system endobiotic, consisting 

 usually of a subsporangial apophysis with or without an unbranched 

 or branched broad rhizoid; resting spore epibiotic, sessile, thick-walled, 

 formed from the body of the receptive thallus after conjugation with a 

 usually smaller contributing thallus by means of a conjugation tube 

 produced by the smaller plant, germination not observed. 



A genus the species of which are known only as parasites of green 

 algae and diatoms. 



