282 THE LOWER FUNGI— PIIYCOMYCETES 



discharged. The almost total suppression of sporangiospore 

 formation, coupled with the presence of the phenomenon of 

 discharge, indicates that the asexual stage in this order has 

 reached a higher point in development than is seen elsewhere in 

 the Phycomycetes. The conidiophore arises as an outgrowth 

 from a cell of the filamentous mycelium or from a hyphal body 

 and, except in Massospora, pushes through the host tissue or 

 substratum to the surface, where it forms its conidia in the air. 

 The conidiophores stand finally in tufts or in a definite palisade 

 layer or hymenium which may cover a considerable area. In 

 Massospora the conidia reach maturity within the host and fall 

 away from the condiophores instead of being discharged. 



The hyphal bodies sometimes assume thick walls and function 

 as chlamydospores. Definite globose, thick-walled resting spores 

 (zygospores or azygospores) are formed in most species. Zygo- 

 spores result from a true sexual conjugation of a pair of hyphal 

 bodies or cells of the filamentous mycelium. Azygospores are 

 formed without conjugation from one such cell. These resting 

 spores are formed either within one of the fusing cells (Basidio- 

 holus, Conidioholus) or in an outgrowth or bud from one of the 

 cells or from the canal at their point of union as in Piptocephalis of 

 the preceding order. Little is known concerning germination of 

 the resting spore in the group. It probably puts out a tube which 

 functions as a conidiophore or grows directly into mycelium. 



The order as here treated consists of the single family Ento- 

 mophthoraceae, including five genera. The genus Basidioholus 

 was removed from this family by Gaumann (1926), and made 

 the basis of another family Basidiobolaceae. Later Gaumann 

 and Dodge (1928) incorporated all the forms in the single family 

 Entomophthoraceae but recognized two subfamilies, Basidio- 

 boleae and Entomophthoreae. Lakon (1926) emphasizes the 

 desirability of retaining Basidioholus in the family on account 

 of intergrading characters in various forms. The writer feels 

 that little if anything is to be gained by splitting the group. 



No general monograph of the species of the world has yet 

 been prepared. The paper on American forms by Thaxter (1888) 

 is the most extensive discussion of the group, and is excellently 

 illustrated. 



The most widely distributed and generally known species of 

 the order is Empusa muscae, parasitic in the house fly. In late 

 summer and autumn flies attacked by this fungus may be seen, 



