ZYGOMYCETES 



125 



(in the latter extramatrical) takes place between hyphal ends (Fig. 

 76, 5, 8, 9). In E. sepulcralis within or without the host, two hyphae 

 form lateral outgrowths which often dissolve the separating wall without 

 abjunction from the hyphae. The zygote does not arise at the point of 

 fusion but on a copulation branch (Fig. 76, 6 and 7). E. rhizospora forms 

 its zygospores extramatrically like E. echinospora; in it the remaining 

 extramatrical hyphae become sclerotia and without being dissolved 

 change into a horny, chocolate-colored tissue which holds the spores 

 firmly together (Fig. 77). 



In many Entomophthoreae only hypnospores are known. These 

 are provisionally placed in Tarichium (Lakon, 1915). 



The relation to the other Zygomycetes, especially the Mucoraceae, 

 is still obscure. As regards their asexual fructification they appear 



Fig. 77. — Entomophthora rhizospora. 1. Group of extramatrical hyphae, forming 

 zygospores. 2. Old hardened hyphae which surround the zygospores with rhizoidal 

 processes. (X 290; after Thaxter, 1888.) 



below these as they possess no conidiophores but only conidial hyphae. 

 As regards their sexual fructification, however, they are on the same 

 level. Possibly we have to do with two parallel unrelated lines. 



Summary. — The thallus develops from a uninucleate, centrally 

 organized thallus to a multinucleate, eventually septate, mycelium whose 

 hyphae are adapted to independent existence. The organs of repro- 

 duction, sporangia and gametangia, however, remain essentially the 

 same in their gross characters. In comparison with the thallus, they 

 require a continually smaller supply of material and hence one individual 

 can form increasingly larger numbers. By a premature end of develop- 

 ment, the individualization of the daughter cells is suppressed; the 

 sporangia become conidia, and their daughter cells assume the task of 

 propagation; the gametangia remain equally coenocytic, a continually 

 decreasing; number of their nuclei function as sexual nuclei, and they 



