262 BOTANICAL GAZETTE ' [march 



well developed, but it usually ruptures before the stem is much 

 elongated (fig. lo) and forms a rather slight ring on the stem. 

 The subsequent elongation of the stem results in the position of 

 the ring near the stem base. 



Discussion 



As Atkinson (5) has said, the few species of Agaricaceae with 

 endogenous origin of the hymenophore, whose development has 

 been studied, fall into 3 groups, based on the order of differentia- 

 tion of the pileus, stem, and hymenophore fundaments in the 

 carpophore. In the first of these groups the pileus primordium is 

 differentiated first. This group is represented by Hypholoma sub- 

 lateritium, H. fasciculare, Amanita rubescens, and Amanitopsis 

 vaginata. A second group includes those species in which the stem 

 primordium is first differentiated, this being followed by the differ- 

 entiation of the pileus primordium and later of the hymenophore 

 primordium. This group is represented by Lepiota cristata, L. semi- 

 nuda, and Rozites gongylophora. In the third group the hymeno- 

 phore primordium appears while the remainder of the carpophore 

 is seemingly undifferentiated, and the distinction of pileus and stem 

 comes later. In this group we find Agaricus campestris, A . arvensis, 

 A. Rodmani, Armillaria mellea, and Stropharia ambigua. 



Stropharia epimyces, from its mode of development, is to be 

 placed in the third group mentioned. This may be taken as 

 additional evidence, if any further evidence is needed, that our 

 plant belongs to the genus Stropharia and not to Panaeolus, as was 

 first thought by Peck, since the type of development is the same 

 as that of the only other species of Stropharia that has been studied 

 (11) and of species of the closely related genus Agaricus. 



Stropharia epimyces as it occurs at Urbana agrees in detail with 

 the description given by Atkinson (i, 2), except that it occurs on 

 Coprinus comatus instead of C. atramentarius as did those collected 

 by Atkinson. The recognition of the host plant was easy in this 

 case since there were many uninfected plants growing along with 

 the infected ones, and also many plants which had "pinhead" 

 and "button" stages of the parasite on them but were not deformed 

 to such an extent as to be unrecognizable. The spores are dis- 

 tinctly purple-black in color. The annulus is often not very prom- 



