CHYTRIDIALES 275 



on both diatoms and rotifer eggs. Arbitrarily, however, and with 

 some justification on morphological and physiological grounds, this 

 inhabitant of nematodes is segregated for the present from R. sphaero- 

 carpum. 



6. Domjan (1936: 42, pi. 1, figs. 3-4, 13, 26), on Spirogyra, Zygnema, 

 and C/osterium, Hungary. The sporangia and resting spores resemble 

 somewhat those of Rliizophydium sphaerocarpum, but the rhizoidal 

 system is richly branched and extensive. 



7. Tokunaga (/or. c/Y., pi. 11, fig. 7), on Cladophora sp., Japan. 

 The rhizoids are too richly branched for this species. The fungus re- 

 sembles closely Domjan's organism. 



8. Rliizophydium sphaerocarpum var. cryophilum Laszlo Berczi (in 

 Kol, 1942: 29, figs. 4-5), on the snow alga Ancyclonema nordenskioldii, 

 Alaska. This form is too little known to be recognized. Although its 

 sporangium resembles that of R. sphaerocarpum, its rhizoid is branched. 



The chytrid supposed by Dangeard ( 1 890-9 lc: 244, pi. 16, fig. 9) 

 to be Zopf's species and called Chytridium sphaerocarpum by Dan- 

 geard is operculate and has been retained in Chytridium. 



Rhizophydium vaucheriae de Wildeman 



Mem. Herb. Boissier, 1900 (15) :6, Bull. Acad. Roy. Belg. (Sci.), V, 17:285, 



fig. 1, 1-10. 1931 



Sporangium sessile, spherical, 26-50 [jl in diameter, with a broad 

 prominent apical papilla, wall somewhat thickened, colorless, smooth; 

 endobiotic part consisting of an unbranched rhizoid; zoospores spher- 

 ical, 1.5 \x in diameter, with a conspicuous colorless globule, escaping 

 successively through a large apical pore formed upon the dissolution 

 of, or rarely the dehiscence of, the apical papilla, the empty spo- 

 rangium strongly urceolate, the irregular discharge pore with a slightly 

 recurved margin; resting spore not observed. 



Parasitic, often in large numbers, on the oogonia of Vaucheria 

 sessi/is, coll. Massart, Belgium. 



Further observations on the process of zoospore discharge are nec- 

 essary. Typically, the conspicuous papilla is dissolved, but on rare 

 occasions it is said to persist and to be thrown back as a sort of oper- 

 culum. De Wildeman believes dissolution of this cap occurs at a varying 



