CHYTRIDIALES 487 



Sporangium with or without a simple apophysis, developing 

 from all or part of zoospore cyst 

 Sporangium always completely fertile 



Resting spore within the substratum Chytridium, p. 488 



Resting spore external to the substratum 



Resting spore asexually formed; zoospores typically un- 

 dergoing collective swarming after discharge 



Chytriomyces, p. 537 

 Amphicypellus, p. 546 

 Resting spore sexually formed after conveyance of the 

 male gamete by means of a tube into the female gam- 



etangium Zygorhizidium, p. 547 



Sporangium frequently with a sterile basal stalk 



Rhopalophlyctis, p. 553 

 Sporangium with a compound apophysis consisting of a primary 

 cell beneath the sporangium and a series of intercommuni- 

 cating catenulate segments which give rise distally to rhi- 

 zoids; an unexpanded portion of zoospore cyst always pres- 

 ent on the sporangium Catenochytridium, p. 555 



Rhizoidal system arising from more than one place on surface of 

 sporangium; the latter with one or more discharge papillae 



Karlingiomyces, p. 559 

 Sporangium or resting spore formed as a lateral walled-off out- 

 growth of the distal external part of the cylindrical main axis; 

 rhizoids broad and tubular, the whole plant large 



Macrochytrium, p. 565 

 Sporangium formed from the tip of the germ tube of the zoospore, 

 within the substratum; resting spores always endobiotic 



Subfamily Endochytrioideae, p. 567 

 Rhizoidal system not catenulate 



Sporangium attached directly to the rhizoidal system 



Endochytrium, p. 568 

 Sporangium arising as an outgrowth of an apophysis to which is 



attached the rhizoidal system Nephrochytrium, p. 573 



Rhizoidal system catenulate 



Rhizoids arising from a single place on the sporangium; the latter 



cylindrical and stalked Cylindrochytridium, p. 577 



Rhizoids arising from several places on the sporangium; the latter 

 spherical, oval, or irregular, but not cylindrical or stalked 



Truittella, p. 578 



