KEYS TO THE FAMILIES AND MORE IMPORTANT GENERA OF MUCORALES 185 



Ke]) to the Genera of Family Choanephoraceae 



Primary sporangia with columella, terminal to an upright sporangiophore. 

 Sporangioles borne on the surface of spherical heads clustered at the upper 

 end of special sporangioliferous hyphae. 

 Sporangioles containing 3 (to 6) spores, resembling those of the sporangium. 



Blakeslea 

 Sporangioles one-spored, indehiscent. Sexual reproduction of the Mucor type. 



Choanephora 



Primary sporangia lacking, only the indehiscent one-spored sporangioles formed. 



Sporangioles borne on rounded heads on short lateral branches, mostly rough. 



Fertile hyphae in a dense, tangled mass of aerial mycelium and bearing the 



heads of sporangioles terminally and on lateral branches without regular 



order, sporangioles smooth or rough, round or ovoid. Sexual reproduction 



of the Mucor type. Cunninghamella 



Fertile hyphae upright, forking into S-shaped branches, sterile at the tips 



but bearing heads of spherical rough sporangioles on short lateral branches. 



Sigmoideomyces. 

 Fertile hyphae upright, supported at the base by mostly four spreading 

 branches and at the top dichotomously dividing several times into branches 

 sterile at their tips but bearing on short lateral branches the heads of 

 spherical rough sporangioles. Thaynnocephalis 



Sporangioles small, ellipsoidal, smooth, borne on an elongated head which be- 

 comes septate at maturity and with the sporangioles resembling a head of 

 Typha. Mijcotypha 



Key to the Genera of Family Mortierellaceae 



Sporangiophores erect, unbranched, or branched. Mortierella 



Sporangiophores creeping. Herpocladiella 



Sporangiophores short and unbranched along the sides of a hypha of indeter- 

 minate growth. Dissophora 

 {Haplosporangitmi possibly belongs to this family.) 



Key to the Genera of Family Piptocephalidaceae 



Main sporangiophores with large heads covered by the radiating narrow spo- 

 rangia. 

 Main sporangiophore branched, sporangia arising directly, not from sterigmata. 



Syncephalastrum 

 Main sporangiophores stout, not branched, tapering toward the terminal head. 

 In most cases sporangia borne on sterigmata, one or more on each. 



Syncephalis 

 Main sporangiophores branching freely above by true or false dichotomy with 

 small heads or only slight enlargements from which the sterigmata arise. 

 Branches straight, sterigmata one-celled. Piptocephalis 



Branches more or less spirally curved, sterigmata two-celled, two-celled spo- 

 rangia arising from the apex of each cell. Dispira 

 Main sporangiophores with small or medium size heads terminal to the hyphae 

 and their branches, bearing on all sides two-celled sporangioles. Origin of 

 these latter not definitely worked out and relationship uncertain. 



Spinalia 



