492 AQUATIC PHYCOMYCETES 



Sporangium without apical teeth 



Sporangium wall with part of the case of the zoospore persisting 

 as a small protuberance 

 Sporangium arising as an apical outgrowth of the zoospore 

 case; rhizoids lacking; on Vaucheria 

 Sporangium typically perpendicular to host wall, sym- 

 metrical; resting spores unknown C. cejpii, p. 512 



Sporangium typically inclined to host wall, strongly bent 

 and sometimes twisted; resting spores abundant, 



sexually formed C. scxuale, p. 513 



Sporangium arising as a more or less lateral outgrowth of the 

 zoospore cyst; with or without rhizoids; on green algae 

 Sporangium ovoid, ellipsoid, pyriform, or subspherical; 

 protuberance either colorless or amber or brown 

 Protuberance colorless 



Resting spore smooth-walled; sporangium wall rigid 

 after discharge of zoospores 

 Sporangium ovoid, ellipsoid, or pyriform; protuber- 

 ance basal or slightly elevated; operculum 

 small, rhizoids branched, tapering 



C. schenkii, p. 514 

 Sporangium narrowly obovoid; protuberance basal; 

 operculum small ; rhizoid tubular and unbranch- 



ed C. oecJogonii, p. 5 16 



Sporangium spherical, subspherical, or ellipsoidal; 

 protuberance subapical or lateral; operculum 



large C. kolianum, p. 516 



Resting-spore wall covered by straight, bent, sharp or 

 blunt, or clavate outgrowths; sporangium wall 

 collapsing after spore discharge . . . C stellatum, p. 517 

 Protuberance amber-colored or brown; sporangium 



ovoid or subspherical C. aggregation, p. 518 



Sporangium utriculate or somewhat tubular, dorsally gib- 



bose; protuberance colorless C. gibbosum, p. 519 



Sporangium wall entirely smooth 



Sporangium transversely placed on the substratum, ovate or 



ellipsoidal; on Chlorobotrys C. chlorobotrytis, p. 519 



Sporangium more or less upright 



Sporangium broadly obovoid, often asymmetrical; apoph- 

 ysis spherical, without rhizoids; on Characiopsis 



C. scherffelii, p. 519 

 Sporangium spherical, subspherical, ovoid, urceolate, pyri- 

 form or citriform 



