CHYTRIDIALES 199 



21 (jl), outer wall irregularly reticulate, bearing from twelve to twenty- 

 four straight or somewhat curved hyaline tapering spines up to 22 (x 

 long (mostly about 12 fx), sorus smooth-walled, spherical or ovoid; 

 sporangia from eight to twenty-four or more, usually polygonal, 

 sometimes pyramidal with rounded base and truncate apex, 8.4 (a 

 high by 9.6 (i. broad; zoospores numerous, subspherical or ovoid, 

 1 (jl thick, with one or two globules and a slender flagellum, escaping 

 through a pore formed in the narrow apex; resting spore subspherical, 

 16-21 (j. in diameter, somewhat angular, thick- walled, with long taper- 

 ing spines, pale yellow brown, upon germination functioning as a 

 prosorus. (Modified from Couch.) 



Parasitic in Spirogyra sp. (Couch, he. cit.), United States; Mouge- 

 otia sp., Kobayashi and Ookubo (as Olpidiopsis sp.) (1954b: 571, 

 fig. 12), Japan. 



As in Micromyces zygogonii the thallus and prosorus are uninucleate 

 (Fig. 16 A-B, p. 196), nuclear division taking place only in the sorus. 

 Couch (op. cit.) also presents evidence that the resting spore upon ger- 

 mination is uninucleate. There is some reason to believe that, as in 

 Synchytrium, the so-called "zoospores" may behave as planogametes 

 and fuse in pairs, giving rise to a planozygote which presumably pene- 

 trates the alga and forms the resting spore. What is known of the cy- 

 tology of Micromyces indicates that it closely resembles Synchytrium. 



Further observations are needed on the method of infection. Earlier, 

 Couch (1931) had stated that in Micromyces zygogonii the zoospore 

 softens the wall and forms a perforation through which it flows. Wheth- 

 er or not a cyst is left on the surface has not been determined. In 

 view of the small size of the zoospore such a cyst, if formed, would 

 probably be a difficult structure to observe. 



Micromyces mirabilis (Canter), comb. nov. 

 (Fig. 16 H, p. 196) 



Micromycopsis mirabilis Canter, Trans. Brit. Mycol. Soc, 32: 82, figs. 6-7, 

 pi. 11, figs. 1-3. 1949. 



"Prosorus (resting spore?) very elongate, 75 x 20 to 112 x 57 ;j.; 

 less elongate, 21 x 12.8 to 67 x 55 \i or spherical, 12 x 10 to 37 x 



