234 AQUATIC PHYCOMYCETES 



Globule of zoospore more than half the diameter of body 



of zoospore R. macrosporum, p. 259 



Sporangium predominantly ovoid or somewhat citriform 

 Papilla obliquely placed; primarily on Tribonema 



R. asymmetricum, p. 260 

 Papilla terminal; primarily on green algae 



Papilla small; resting spore unknown R. mammillatum, p. 260 

 Papilla broad; resting spore sexually formed 



R. uniguttulum, p. 262 

 Discharge pore?, one or two, terminating very distinct dis- 

 charge tubes 



Discharge tube single, apical R. ampullaceum, p. 262 



Discharge tubes two, opposed (occasionally one) 

 Tubes narrow, hornlike; rhizoids branched 



R. rostellatum, p. 263 

 Tubes broad, giving the sporangium a triangular ap- 

 pearance; rhizoids unbranched R. haynaldii, p. 264 



Sporangium wall ornamented 



Sporangium wall bearing long, slender, branched or un- 

 branched hairs on its upper part; on green algae 



R. chaetiferum, p. 264 

 Sporangium wall bearing short, simple, bifurcate, or dichot- 

 omously branched spines; on keratinized tissues 



R. keratinophilum, p. 265 



In marine waters; on Codium R. codicola, p. 266 



Sporangium predominantly spherical at first and urceolate after dis- 

 charge, or pyriform, conical, or flask-shaped Section II, p. 268 



Sporangium spherical at first but urceolate (occasionally pyriform) 

 after discharge 

 Rhizoids branched 



On pollen R. pollinis-pini, p. 268 



On Ophiocytium R. sciadii, p. 271 



Rhizoids little if at all branched 

 On algae 



Sporangium very small (up to 7 jx in diameter); on diatoms 



(Asterionella) R. schroeteri, p. 272 



Sporangium larger; on blue-green or green algae 

 On blue-green algae {Oscillator id) 



R. oscillator iae-rubescentis, p. 272 

 On green algae 



Sporangium 6-18 \i in diameter by 20 \x high; on various 

 green algae, primarily Conjugatae 



R. sphaerocarpum, p. 273 



