80 THE LOWER FUNGI— PHYCOMYCETES 



Synchytriaceae 



Mycelium wholly lacking; thallus intramatrical, provided from 

 an early period with a membrane, at maturity either functioning 

 in its entirety as a resting sporangium, or divided by cleavage 

 planes to form a sorus of sporangia enclosed in a common soral 

 membrane; zoospores uniciliate; cilium at the posterior end of 

 the spore. 



Key to Genera of Synchytriaceae 



I. Resting spore relatively large; parasites in higher plants. 



1. Synchytrium, p. 80 

 II. Resting spore very small; parasites in algae. 



2. Micromyces, p. 87 



I. Synchytrium de Bary & Woronin (1863: 22). 



Probably no other genus of the Chytridiales is as widely known 

 as Synchytrium. It is cosmopolitan in range, and several of its 

 members are of considerable economic importance. The species 

 are all parasitic in higher plants and cause noticeable galls. 



The most extensive and satisfactory taxonomic treatment is 

 that of Tobler (1913), but the monographs of Fischer (1892: 45) 

 and von Minden (1911: 287) will also be found useful. Much 

 work remains to be done before we will have a satisfactory 

 knowledge of specific limits. 



The genus may be split into four apparently natural groups of 

 species, and these are treated here as subgenera. 



I. Resting spores unknown; mature thallus functioning as a summer sorus 

 of thin-walled sporangia; sporangia delimited within the thallus wall 

 and freed by its rupture. 



subgenus Woroninella 



II. Resting spores known. 



A. Life cycle embracing summer sori and the resting spore; the latter 



in germination functioning as a single sporangium and freeing 

 swarmspores directly without the extrusion of a vesicle. 



1. The sporangia of the summer sorus delimited within the 



thallus wall and freed by its rupture. 



subgenus Eusynchytrium 



2. The thallus functioning as a prosorus and extniding a thin- 



walled vesicle into which the protoplast flows antl in which 

 the sporangia are then delimited. 



subgenus Mesochytrium 



B. Summer sori not formed; resting spore in germination functioning 



as a prosorus, and extruding the endospore as a thin-walled 

 vesicle in which the sporangia are then delimited. 



subgenus Pycnochytrium 



