CHYTRIDIALES 



87 



open aecidium-like sori and in the absence of the resting spore 

 stage it would seem that Gaumann's erection of the subgenus 

 Woroninella was warranted. It is possible that further study- 

 will make desirable merging the group with Eusynchytrium. 



North American species of Synchytrium not listed above 

 because of their uncertain position in the genus include the 

 following. 



S. asari Arthur & Holway — on Asarum. 



S. caricis Tracy & Earle — on Carex. 



S. innoviinntum Farlow — on Malacothrix. 



S. nigrescens Davis — on Aster. 



S. scirpi Davis — on Scirpus. 



S. vaccinii Thomas — on Vaccinium, Kalmia, Cassandra, etc. 



Fig. 19. 



Micromyces zygoyoni Daiigourd in Zygogonium. {After Dangeard 

 1889.) 



2. Micromyces Dangeard {Le Botaniste, 1:55, 1889). 



A small and imperfectly understood genus included here as 

 a doubtful member of the family. The genus was based by 

 Dangeard on a single species, M. zygogoni Dang. (Fig. 19), found 

 in France in the cells of the alga Zygogonium. Subsequently 

 several other species have been described from other algae. 

 These include M. mesocarpi DeWildeman in Mesocarpus in 

 Belgium, M. spirogyrae Skvortzow in Spirogyra in China, and 

 M. petersenii in Mougeotia in Czechoslovakia. 



The mature thallus is a small sphere. It becomes invested 

 in a coarsely spiny membrane, and functions as a resting spore. 

 In germination it either frees zoospores directly, or, as in the 

 subgenus Pycnochytrium of Synchytrium, its contents pass into 

 a thin-walled vesicle and there form a small sorus of sporangia 

 which in turn form zoospores. 



