116 COMPARATIVE MORPHOLOGY OF FUNGI 



tangium, there is a large nucleus which probably has migrated in from 

 the periphery (Fig. 69, 4). The remaining nuclei withdraw toward the 

 base, and are separated from the upper part by a septum. The terminal 

 uninucleate cell corresponds to the gametangium of the Mucoraceae, 

 the basal multinucleate cell to the suspensor. The nuclei which do 

 not withdraw into the suspensor at the right time, degenerate. In 

 another less well-known species, E. pisiformis (E. sphagnophila) , copula- 

 tion is isogamous (in contrast to E. lactiflua) and all gametangial nuclei 

 participate in the sexual act, so that, as in the Mucoraceae, many fertili- 

 zations occur between the two gametangia, rather than a single game- 

 tangial nucleus serving as a sexual nucleus (Atkinson, 1918). Thus 

 both the sporangia and gametangia of Endogone seem to be directly 

 connected with the Mucoraceae. 



Almost simultaneously with or directly after the formation of the 

 basal septa, the separating walls disappear at the tips of the game- 

 tangia and the male nucleus passes over into the female game- 

 tangium (Fig. 69, 5 and 6). Near the copulation opening, a thin walled 

 sac grows out on the female gametangium. The contents of both 

 gametangia migrate into this sac which enlarges and becomes a zygo- 

 spore; its membrane thickens, plugs the basal pore and forms a thick 

 cartilaginous endospore. This apparently corresponds to the cartilagi- 

 nous layer of the zygospores of the Mucoraceae. Furthermore, numerous 

 verticillate, multiseptate, adherent sheath hyphae surround it (Fig. 

 69, 7), thicken their walls considerably and form in cross section the 

 so-called halo (Fig. 69, 8). Functionally, this is possibly a substitute 

 for the carbonaceous layer of the Mucoraceous zygospore. In this 

 species, apparently, the nuclei fuse only on germination; in other species, 

 such as E. pisiformis (E. Ludwigii), fusion occurs shortly after copulation. 

 The germination of the zygospores is unknown. Perhaps it takes place 

 only after the spores have passed through the digestive tracts of animals. 

 In eleven other mostly northern species, as E. microcarpa and E. 

 macrocarpa, the zygospores are replaced by similar multinucleate azygo- 

 spores or chlamydospores (Fig. 68, 6 and 7). In E. fasciculate, the 

 chlamydospores arise from a plexus of clearly defined, thick-walled, 

 interlacing hyphae, forming a core from which radiate short, irregular 

 sporiferous branches. Thus the chlamydospores are at first associated 

 in racemose clusters. In the same fructification, the zygospores are 

 formed as a result of homothallic heterogamous conjugation, and are in a 

 scattered group, not in racemose clusters. In the tropical genera, 

 Sclerocystis (Xenomyces, Akermannia) and Glaziella (G. aurantiaca, 

 Endogonella borneensis) the chlamydospores are arranged in special 

 layers within the fructification (Fig. 68, 8 and 9). 



The Endogonaceae, especially E. lactiflua, show essentially the same 

 characters which we have come to know in the Mucoraceae, only they 



