232 THE AGARICACEAE OF MICHIGAN 



x 6 niicr., smooth, obtusely pointed, black. Sterile cells on edge of 

 gills, linear, subcapitate, 30-40 x 4-5 niicr. ODOR none. 



Gregarious. On horse dung and soil, in woods pastured by horses. 

 Ann Arbor. October. 



This is close to P. sphinctrinus Fr. in most of its characters, but 

 differs in its much smaller spores and in the lack of a persistent, 

 appendiculate veil. The surface portion of the pileus has the same 

 structure that is given by Godfrin (1. c.) for P. sphinctrinus. 



AMAUROSPORAE 



Psalliota Fr. 

 (From the Greek, Psallion, a ring or collar.) 



Purple-brown-spored. Stem fleshy, separable from the pileus, 

 provided with a persistent or evanescent annulus. Gills free, usually 

 pink or pinkish in the young stage. 



Fleshy, mostly compact and large mushrooms, growing on the 

 ground in woods among fallen leaves, etc., or on lawns, pastures, 

 open ground or cultivated fields. They correspond to Lepiota of 

 the white-spored group. They are all edible, the larger ones being 

 among the best known and most widely used of edible mushrooms. 

 Several species have been cultivated a long time and are of con- 

 siderable commercial importance, especially in Europe. (See re- 

 marks under P. campestris.) 



The PILEUS is glabrous, fibrillose or fibrillose-scaly, either white 

 or whitish or dark colored by the color of the fibrils on its surface; 

 these fibrils compose a thin layer on the very young cap, and as the 

 cap expands are broken up, except at the slow-growing center, into 

 fibrillose scales. The young cap of these species is therefore much 

 more uniformly colored than later in the expanded stage. The sur- 

 face of the whitish species is often stained somewhat with yellowish 

 of rufescent hues when bruised or in age. The size varies; most spe- 

 cies may become quite large, P. subrufescens reaching a size of 20 

 cm. across the cap ; a few are quite small. The surface is dry, or it 

 may be slightly viscid as in P. cretacella. The GILLS are free, as 

 in Lepiota. When the button is quite small it is white, but in some 

 species, e. g. P. campestris, becomes pink quickly. This character 

 has been used to separate the species, but is a difficult point for be- 

 ginners to determine. As the spores begin to take on color, the pur- 



