518 AQUATIC PHYCOMYCETES 



(1926a: 233, pi. 10, figs. 118-124), Hungary; Zygnema sp., Koch (he. 

 cit.), United States. 



Koch's (op. cit.) careful study of the development of this species 

 clearly shows that it had a very delicate operculum and that its resting 

 spores were asexually formed. 



Chytridium aggregatum Karling 

 Mycologia, 30: 302, text figs. 1-19. 1938 

 (Fig. 31 K, p. 496) 

 "Thalli numerous and gregarious, partly intra- and extramatrical, 

 eucarpic. Zoosporangia extramatrical, formed as a lateral or slightly 

 basal outgrowth from the encysted zoospore case and delimited from 

 the apophysis by a cross wall at maturity; hyaline, smooth, oval, egg- 

 shaped, subspherical, 4x6^-10x18^, with a conspicuous amber or 

 brown protuberance, the zoospore case, near the base, and an apical 

 or slightly sub-apical exit papilla; operculum spherical, 4-8 ja, or slightly 

 oval Zoospores hyaline, conspicuously uniguttulate, spherical, 3-4.5 fx, 

 posteriorly uniciliate; emerging in a globular mass and lying quiescent 

 near the exit papilla for a few moments before moving apart; motility 

 confined to a few jerky motions and amoeboid movements; settling 

 down on the host cell and germinating in a mass in the vicinity of the 

 zoosporangium. Apophysis intramatrical, spherical, 5-10 [x, oval, broad- 

 ly spindle-shaped, elongated and occasionally constricted. Rhizoidal 

 system well developed and branched, extending often to a distance of 

 110 ji; main axis 3-4 u. in diameter. Resting spores intramatrical, 

 hyaline, spherical, 5-14 jx, oval, slightly citriform, 6 x 9[x-12 X 14 u., 

 somewhat depressed, and occasionally flattened or constricted, usually 

 with a single large refractive globule and a 2.5-3 p thick, smooth wall; 

 germination unknown" (Karling, he. cit.). 



Saprophytic on Spirogyra crassa, Oedogonium sp., and Cladophora 

 sp Karhng(/oc. cit.), Cladophora, Sparrow (1943: 345), United States. 



Differing from Chytridium schenkii only in the brown or amber zoo- 

 spore case. The gregarious habit is not constant, and the sporangia 

 have been found many times in Michigan occurring singly on algal 

 cells. 



