10 BROOKLYN BOTANIC GARDEN MEMOIRS 



there is first a nuclear fusion in pairs, perhaps some of the nuclei 

 degenerating. If this is confirmed the situation in E. sphagnophila 

 agrees in this respect with that in the Mucorales. It appears also that 

 later, when the nuclei lie in a peripheral zone, they undergo at least 

 one division. At the present stage of the investigation the possibility 

 is not excluded that fusion of nuclear pairs does not occur. It is also 

 possible that after the division of the nuclei in the peripheral zone of 

 the zygote all but two may degenerate, the two selected ones later 

 uniting to form the fusion nucleus. This would bring E. sphagnophila 

 more nearly in line with the process in E. lactiflua as described- by 

 Bucholtz, the selection of the sex nuclei being postponed to a late 

 period in E. sphagnophila. I do not think, however, that this is the 

 case, but am inclined rather to believe that there is multinuclear fusion 

 in pairs, ^ similar to that which takes place in the Mucorales as de- 

 scribed by Gruber (1901) in Sporodinia, by Dangeard (1906) in Sporo- 

 dinia, and by Moreau (1911-1913) in Rhizopus, Zygorhyncus and 

 Sporodinia. That in certain species of Endogone there is fusion of 

 but one pair of sex nuclei in the zygote, while in other species there 

 may be fusion of several pairs of sex nuclei, is not incomprehensible 

 in view of the nuclear process in fertilization in Cystopus (See Stevens 

 1899, 1 901), where in C. hliti and portulacae there are fusions of many 

 pairs of sex nuclei in the egg, while in other species there is fusion of a 

 single pair of sex nuclei. 



There is another feature in E. lactiflua which is paralleled in 

 certain of the Zygomycetes. This is the hyphal envelope which 

 encloses each zygote. Crude tendencies to such an envelope are 

 present in Phycomyces and Absidia of the Mucorales and in Empiisa 

 rhizospora of the Entomophthorales (Thaxter, 1888), while in Mor- 

 tierella there is a well-developed envelope. In no other species of 

 Endogone, however, is such an envelope around each zygote known, 

 not even a rudimentary one. In this respect E. lactiflua represents a 

 more advanced stage of evolution, which is manifested also in the 

 origin of the resting zygote as a distinct outgrowth of the larger 

 gametange. This species may possibly represent the type of a distinct 

 genus, so widely does it depart in these two respects from all the 

 other known species. 



There is another feature, however, in which Endogone departs 

 widely from any other known phycomycete. The mycelium and 

 numerous zygotes ("resting" spores or "sporangia" in the partheno- 

 genetic species) are united into a compact and distinct fruit body, or 



^ According to Leger (1896) in Sporodinia grandis, and according to Miss McCor- 

 mick (1912) in Rhizopus nigricans, ail nuclei but two degenerate in the zygote, but 

 this has not been confirmed. 



