2 BROOKLYN BOTANIC GARDEN MEMOIRS 



doubtful, however, if true sporulation has ever been observed. In 

 dead resting spores the contents often segregate into a number of 

 large, rounded or elliptical bodies. In E. reniformis the single spore 

 in an "ascus" is probably the "resting spore" itself, while in the 

 species described as having numerous minute sporidia in an ascus 

 (often with an interrogation), the supposed sporidia are probably the 

 numerous fat bodies conspicuous in some species. 



Origin and Development of the "Resting Spores" in 

 Endogone lactiflua Berk. 



Character of the mycelium. — The only important contribution to 

 development in the genus Endogone, thus far, was made by Bucholtz 

 in 1912, in his study of Endogone lactiflua. This species is subter- 

 ranean and occurs in various parts of Europe. The fruit bodies range 

 in size from 4 mm. to 2 cm. The material studied by Bucholtz was 

 found in a plantation of Abies sihirica in Livland, Russia. The 

 mycelium is coenocytic, profusely branched, the hyphae following a 

 very sinuous course, but the general direction is radial and toward the 

 periphery. It is non-septate, true cross walls being formed only in 

 connection with the reproductive organs, though false cross walls are 

 occasionally found in the vegetative hyphae. The hyphae vary 

 greatly in diameter, in general becoming more slender toward the 

 periphery of the fruit body, but irregularities in the form of swellings 

 occur. Terminal branches on the interior are often clavate. Sack- 

 like enlargements occur from which numerous branches often diverge. 

 The walls of the hyphae are thick. The nuclei are minute, very 

 numerous, and lie in a parietal layer of cytoplasm. 



The progametes and conjugation. — The progametes are clavate and 

 of unequal size. They lie nearly parallel and their walls fuse at the 

 lateral point of contact a short distance from the free ends. The 

 nuclei in the progametes, lying near the periphery become larger, 

 more distinct, and undergo one division. The nuclei now retreat from 

 the terminal portion of each progamete and all except one are excluded 

 from each gametangium by a cross wall. A few sterile nuclei some- 

 times remain in the gametangium but soon degenerate. The origin 

 of the selected gamete nucleus in each gametange is not known, but 

 it is probably derived from one of the peripheral nuclei in the pro- 

 gamete, or one of the daughter nuclei after mitosis. These gamete 

 nuclei are much larger than the progamete nuclei, thus maintaining 

 the nucleo-cytoplasmic relation. Each one occupies the center of its 

 gametange. The walls at the point of contact are now resorbed. 

 The nucleus from the smaller gametange (antherid) migrates into the 

 larger one (oogone). 



