EEVISION OF ENDOGONEAE. 293 



for the collection of these and other fungi hypogaei, the recognition of 

 others is surrounded by no such difficulty, since their fructifications 

 may be developed free to the air, on mosses, rotten wood, leaves, dung 

 or other substances above the leaf cover, or emerging from it. 



It seems not improbable that the vegetative hyphae of all the 

 Endogoneae are at first continuous. In a majority of cases, however, 

 the hyphae of sporulating conditions show at least occasional septa, 

 which, in highly developed sporocarps like that of Glaziella, become 

 ver}^ abundant. The spores developed from these hyphae are either 

 zygospores, thick-walled acrogenous chlamydospores or thin walled 

 spores formed endogenously in sporangia. 



The true relationships of the group to other families of fungi have 

 long been a matter of conjecture, as is evident from the terms — asci, 

 sporangia, cysts, vesicles etc. — which have been applied by various 

 authors to the chlamydospores alone. But although the admirable 

 researches of Bucholtz, who first (1912) published an account of its 

 sexual reproduction, have thrown much needed light on its affinities, 

 the group as a whole has been assumed to include forms of considerable 

 diversity. 



The inclusion in a single genus of the zygosporic and chlamydo- 

 sporic types, has hitherto been based entirely on a general resemblance 

 in habit and habitat, and a similarity in the appearance of the two 

 types of spore, and there has been no evidence which would indicate 

 that the two were ever produced simultaneously in the same sporo- 

 carp, or were closely associated in their natural habitats. This as- 

 sumption proves, however, to have been justified; since in a single 

 instance, among the northern forms collected by Professor Jeffrey and 

 herewith described, zygospores and chlamydospores are so intimately 

 associated in the same spore mass, that there can hardly be any 

 question as to their specific identity. 



Although the zygosporic or chlam^'dosporic nature of these spores 

 is usually manifest, except in very old material, it is not always easy 

 in cases where they are surrounded by densely compacted hyphal 

 tissue, to determine whether their origin is sexual or not, the elements 

 involved being so compressed and distorted that conjugating processes, 

 unless very conspicuously differentiated, might well escape notice. 

 This is true for example in Endocjonc incrassafa, Figures 17-19, or E. 

 tuberculosa. There seems, however, at least in the genus Endogone, 

 to be a rather fundamental difference between the two types. In the 

 zygospores, which are usually surrounded by a more or less definite 

 hyphal envelope, an outer wall is present, within which a continuous 



