CHYTRIDIALES 85 



ing the germination of the resting spore. Though it is assumed 

 that it frees swarmspores directly in all the species, it may yet 

 be shown to function in some as a prosorus as in Pycnochytrium. 

 The species of Pycnochytrium may be separated into two 

 groups, those in which the contents of the resting spore are 

 colored (Chrysochytrium) and those in which they are hyaline 

 {Leucochijtrium) . Eight or nine species may be placed in each 

 group with certainty, and there are many other doubtful forms. 

 Throughout the subgenus the resting spore functions in all known 

 cases as a prosorus, the sporangia being formed in an extruded 

 vesicle. Summer sori are not formed in any case. Perhaps 

 the best known species of the subgenus is S. aureum Schroter. 

 While most species are limited to a few hosts this one occurs on no 

 fewer than one hundred and thirty plants representing such widely 

 separated genera as Viola, Ulmus, Trifolium, Solidago, and 

 Mentha. None of the species of Pycnochytrium is of any great 

 economic importance. The following occur in North America: 



S. aureum Schroter — on many hosts. 



S. myosotidis Kiihn — on Lithospermurn. 



S. anemnnes (DC.) Woronin — on Anemone. 



S. anomalum Schroter — on Adoxa. 



S. holwayi Farlow — on Monarda. 



S. mercurialis (Libert) Fuckel — on Oenothera 



S. cinnamomeum Davis — on Ranunculus. 



The three subgenera Eusynchytrium, Mesochytrium, and 

 Pycnochytrium constitute the genus in the older treatments. To 

 these Gaumann (1927: 169) has recently added the fourth, 

 Woroninella. 



Raciborski (1898) erected the genus Woroninella Rac. on a 

 single species, W. psophocarpi Rac, occurring in Java on Pso- 

 phocarpus tetragonolohus DC. He states that it differs from 

 Syyichytrium in the possession of biciliate swarmspores. He 

 regarded it as intermediate between Woronina and Synchytrium. 

 Later he (Raciborski 1900: 7) added another species, W. vulcanica 

 Rac, found on Lespedeza. Both of these fungi cause galls on 

 their hosts, and in general resemble species of Synchytrium. 

 Sydow (1914) then transferred to Woroninella five species 

 previously incorporated m. Synchytrium by other authors including 

 S. aecidioides (Peck) Lag. and S. puerariae (Hennings) Miyabe. 

 The group of forms thus brought together resemble one another 

 in the absence of a thick-walled resting spore and in the powdery 



