296 THE LOWER FUNGI— PHYCOMYCETES 



zygospore. The details of zygospore and azygospore formation 

 are given by Riddle (1906) and Thaxter (1888). 



The genus Empusa was founded by Cohn (1855) on the house 

 fly parasite, E. muscae. The name Empusa had been applied 

 earlier, however, to a genus of orchids, and Fresenius (1856: 882) 

 recognizing this fact proposed Entomophihora to replace Empusa 

 for the fungus genus. Later both names were used together in 

 the Entomophthoraceae by Nowakowski (1884) and Brefeld 

 (1877) for two distinct generic concepts. Nowakowski separated 

 the known entomogenous species into three genera, Empusa, 

 Entomophthora, and Lamia. His treatment was followed by 

 others, including Schroter (1893) who uses it in Engler und 

 Prantl's Die Natiirliche Pflanzenfamilien. In this arrangement 

 Entomophthora is characterized by branched conidiophores, the 

 presence of rhizoids and cystidia, and the production, in at least 

 some species, of true sexually formed zygospores. Empusa, as 

 limited, lacks rhizoids and cystidia, has unbranched conidio- 

 phores, and forms azygospores instead of zygospores. Lamia is 

 said to be intermediate, differing from Empusa chiefly in the 

 possession of cystidia. 



Thaxter (1888) who gave us the first really critical account 

 of the group states that these characters are inconstant, and 

 that border line species make the maintenance of this separation 

 impossible. He unites all the species in a single genus under 

 the name Em,pusa. 



Some years after the appearance of Thaxter's paper Cavara 

 (1899) studied cytologically two species, Empusa muscae and 

 Entomophthora delpiniana, and found that while in the former the 

 conidia are typically multinucleate, they are uninucleate in the 

 latter. Riddle (1906) then investigated seven other species, and 

 found that the conidia of the species which had been referred to 

 Empusa are regularly multinucleate while those of the species 

 placed in Entomophthora are uninucleate. Olive (1906: 202) 

 obtained similar, though less definite, results in five additional 

 species. He showed that the branching habit of the conidiophore 

 is correlated with the uninucleate condition of the conidia. 

 In forms such as Empusa muscae all the nuclei in the vegetative 

 cell from which the conidiophore arises flow out into the conidium. 

 In species like Entomophthora sciarae, on the other hand, the 

 coenocytic conidiophore is divided by septa into uninucleate 

 cells. Each cell then pushes out laterally and elongates until 



