ATKINSON: THE GENUS ENDOGONE 3 



Formation oj the ''resting spore'' and simple zygocar p. —The "resting 

 spore" in Endogone lactiflua is not formed in the immediate zygote 

 resulting from the fusion of the two gametangia nor in the oogone, 

 but in an outgrowth from the latter. During and immediately after 

 fusion of the two gametangia their walls become thickened and firm, 

 so that they can not yield to the pressure from the young growing 

 zygote. As a result there arises a sack-like outgrowth from the end 

 of the oogone into which the cytoplasm from the two gametangia flows 

 accompanied by the two gamete nuclei, the antheridial nucleus fol- 

 lowing the oogonial nucleus. The sac-like outgrowth enlarges into 

 an oval or broadly elliptical resting zygote. A thick, stratified, 

 hyaline, cartilaginous wall is formed next to the primary zygote 

 membrane, which entirely encloses the cytoplasm and other contents, 

 thus separating them from the empty oogone. The two gamete 

 nuclei lie side by side in the center of the zygote but do not fuse until 

 after the resting period, except in a small variety from Germany in 

 which the gamete nuclei fuse at once according to Bucholtz. During 

 the growth and ripening of the zygote it becomes enveloped by slender 

 branches which coil in a more or less spiral manner around it forming 

 a thick cover of small cells, 2-3 cell layers deep, the walls of these 

 cells become greatly thickened and fuse next the zygote, grading out 

 to the thin walls of the surface. Each resting spore, or zygote, with 

 its individual cellular envelope forms a simple fruit or simple zygocarp 

 (zygosporocarp, as Bucholtz terms it). The fruit body of Endogone 

 lactiflua is filled with these simple zygocarps intermingled with the 

 mycelium, and is therefore a compound zygocarp. Germination of 

 the "resting spores" has not been observed. Endogone lactiflua is 

 the only species of the genus in which such simple zygocarps are known, 

 i. e., a fruit body with a single zygote enclosed in its individual envelope. 



Endogone sphagnophila 



In July, 1916, a day or two before the close of a fungus foray 

 organized by Mr. F. C. Stewart at his camp on Seventh Lake, in the 

 Adirondacks, Mr. W. H. Sawyer, Jr., a member of the party, brought 

 in some sphagnum on which were rounded, pulvinate, orange-yellow 

 bodies resembling the plasmodiocarps of certain slime molds. A pre- 

 liminary examination of the internal structure revealed the fact that 

 it was not a slime mold, but apparently a phycomycete with large 

 resting spores having a thick, hyaline, stratified, cartilaginous wall, 

 and orange-yellow content. A pair of stalks, or suspensors, attached 

 to one end of the resting spores in different stages of development, 

 indicated that they had their origin in an interesting type of conjuga- 

 tion. In the afternoon of the same day (July 31, 1916) Mr. Sawyer 



