MU COR ALES 259 



Key to Genera of Choanephoraceae 



I. Sporangium present, accompanied by either sporangiola or conidia. 



.1. Sporangiola present, conidia absent; sporangiospores longitud- 

 inally striate. 



1. Blakeslea, p. 259 



B. Sporangiola absent; conidia present; sporangiospores not striate; 

 conidia striate. 



2. Choanephora, p. 261 

 II. Sporangium and sporangiola absent; conidia present and echinulate, not 



striate 



3. Cunninghamella, p. 263 



1 Blakeslea Thaxter (1914: 353). 



Conidia absent; sporangia of two types (Fig. 92), larger 

 solitary ones possessing a columella, and smaller ones termed 

 sporangiola which lack a columella and occur in considerable 

 numbers over the surface of large, spherical sporangioliferous 

 heads; the two types showing, however, numerous intergrad- 

 ing variations; larger sporangia extremely variable in size, 

 sometimes not larger than the sporangiola; the columella often 

 obsolete; sporangioliferous heads sometimes sohtary at the ends 

 of erect unbranched sporangiophores, but usually in groups of 

 ten or more and terminating branchlets of the subdichotomously 

 branched end of the sporangiophore; sporangiolum typically 

 three-spored, rarely four- or six-spored, attached to the sporangio- 

 liferous head by a small spherical vesicle, when mature falling 

 away carrying the vesicle with it; spores variable in size but in 

 general alike in all types of sporangia, longitudinally striate, 

 provided at each end with a cluster of delicate radiating append- 

 ages like those of the sporangiospores of Choanephora; chlamydo- 

 spores variable; zygospores where known formed between the 

 tips of twining branches. 



The genus contains a single species, B. trispora Thaxter, first 

 isolated as a contamination from a Botrytis culture which in 

 turn had been obtained from flowers of cowpea. It seems to 

 occur as a weak parasite on various plants (Jochems, 1927). It 

 has been shown by Weber and Wolf (1927) to be heterothaUic. 

 It is very closely related to Choanephora, differing chiefly in that 

 the conidia of that genus are here replaced by sporangiola. The 

 spores combine the characters of the sporangiospores and conidia 

 of Choanephora, possessing the appendages of the one and the 

 striations of the other. Thaxter (1914: 357) in a very interesting 



