MU COR ALES 243 



II. Sporangiophore determinate, simple or branched, terminal sporangium 

 always formed; branches only rarely circinate; sporangial wall 

 evanescent. 



A. Sporangiophores arising from aerial, arching stolons which develop 



rhizoids at points of contact with the substratum. 



1. Sporangiophores borne on the arching internodes of the 



stolons between the rhizoid-bearing nodes; sporangia 

 pyriform. 



a. Suspensors of the zygospore provided with prominent 

 circinate outgrowths. 



3. Absidia, p. 244 

 h. Suspensors lacking outgrowths. 



4. Mycocladus, p. 245 



2. Sporangiophores arising in a fascicle from the node of the 



stolon opposite the tuft of rhizoids; sporangia globose. 



5. Rhizopus, p. 245 



B. Sporangiophores arising directly from the mycelium. 



1. Aerial mycelium ornamented with short, lateral, thorn-like 



branches. 



6. Spinellus, p. 246 



2. Aerial mycelium lacking such thorn-like branches. 



a. Sporangiophore branching repeatedly at the apex in a 

 dichotomous fashion; zygospores borne on similarly 

 branched aerial zygophores. 



7. Sporodinia, p. 247 



h. Sporangiophore unbranched, or branching in a monopo- 

 dial or sympodial manner; zygospores borne on the 

 mycelium. 



(1) Sporangiophore unbranched, stiffly erect, with 



metallic iridescence; suspensors of zygospore 

 provided with rigid dichotomously branched 

 outgrowths. 



8. Phycomyces, p. 248 



(2) Suspensors lacking definite outgrowths. 



(a) Gametangia strikingly dissimilar. 



9. Zygorhynchus, p. 249 



(b) Gametangia essentially alike. 



10. Mucor, p. 250 



1. Pirella Bainier (1883: 84). 



Sporangiophore elongating indefinitely, not bearing a terminal 

 sporangium, branching in a cymose manner; the branches cir- 

 cinate, terminated by pyriform sporangia; sporangial wall 

 persistent, incrusted with crystals of calcium oxalate; columella 

 very large, shaped like an elongate hourglass; zygospores 

 unknown. 



The genus is imperfectly known, containing only the type 

 species, P. circinans Bainier. It corresponds with Circinella 



