178 PHYCOMYCETEAE 



are comparable to the sporangioles of some Mucorales or to the sporangia 

 of Piptocephalidaceae needs further study. 



Two groups of fungi placed by their discoverers (Leger and Duboscq, 

 1929b and Leger and Gauthier, 1932) in the families Harpellaceae and 

 Genistellaceae, occur as parasites (possibly only as commensals) in the 

 alimentary canals of various aquatic insects. They consist of slender un- 

 branched flexuous coenocytic hyphae (Harpellaceae) or branched coeno- 

 cytic hyphae (Genistellaceae). They are attached to the host tissues by 

 disk-like or lobed expansions, even finger-like structures in some cases, 

 but do not penetrate through the epidermal layer. The hyphae eventually 

 become septate and bear slender or stout, straight or curved, usually 

 uninucleate conidia, mostly one from each cell of the hypha, often only 

 along one side or in a crown near the apex. Leger and Gauthier (1935) 

 showed that these conidia bear at their point of attachment one (Stachy- 

 lina and Tijphella), two {Genistella) , or four (Harpella) fine filaments 

 which are coiled in the supporting cell and pulled out of the latter as the 

 conidium becomes detached. These appendages may be 3 to 6 times the 

 length of the conidium. Their function is not known but possibly they 

 have something to do with the manner of infection of the host. Sexual 

 reproduction occurs through the union of adjacent cells in the same fila- 

 ment, the thick-walled zygospore being formed in one of these cells as 

 in Basidiobolus or (often in the same species) by the union of conjugation 

 tubes from filaments lying side by side, the zygospores being formed in 

 the center of the enlarged connecting tube or on a stalk growing from 

 this point. In the Harpellaceae the zygospore is spherical while in the 

 Genistellaceae it is biconical or boat-shaped and surmounts a lateral 

 stalk from the uniting tube and is transversely perched at the summit of 

 the stalk. Two parallel filaments of Glotzia centroptili Gauthier may, 

 according to Miss Gauthier (1936), show several conjugations in a scalari- 

 form manner. Leger and his colleagues consider these two families to 

 belong in or close to the Entomophthorales. (Fig. 63.) 



Drechsler (1935, 1936, 1937, etc.) has described numerous species of 

 fungi parasitic on terricolous amoebae and nematodes, placing these in 

 the family Zoopagaceae. This family he places tentatively between the 

 Mucorales and the Entomophthorales. These fungi have various types 

 of haustoria or internal mycelium within the hosts and long slender ex- 

 ternal aerial hyphae from which conidia arise. These external hyphae are 

 nonseptate and multinucleate at first. The conidia arise laterally along 

 the course of these filaments or are terminal and then single or in chains. 

 They are more or less spindle-shaped. The haustorium of Endocochlus, 

 parasitic in Amoeba, is a stout two or more times helicoidally wound 

 structure formed at the end of the infection tube which penetrated the 



