36 CIRCULAR 143, U. S. DEPARTMENT OF AGRICULTURE 
AGARICUS ARVENSIS. HORSH OR FIELD MUSHROOM. (EDIBLE) 
In this species the cap is convex, bell-shaped, then expanded, when young 
floccose or mealy, later smooth, white, or yellowish; the flesh is white; the 
gills white to grayish pink, at length blackish brown, free, close, may be 
broader toward the stem; the stem is stout, hollow or stuffed, may be slightly 
bulbous, smooth; the ring is rather large, thick, the upper part white, mem- 
branaceous, the lower yellowish and radially split. 
The cap is 3 to 5 inches broad; the stem is 2 to 5 inches high, and 4 to 10 
lines thick. 
Agaricus arvensis is to be found in fields, pastures, and waste places. It 
is closely related to the ordinary cultivated mushroom, but differs in its 
larger size and double ring. It is an excellent edible species, the delicacy 
of flavor and texture largely depending, like other mushrooms, upon its age. 
AGARICUS SILVICOLA. FOREST MUSHROOM. (EDIBLE) 
In this species the cap is convex, expanded to almost plane, sometimes 
umbonate, smooth, shining, white, often tinged with yellow, sometimes with 
pink, especially in the center; the flesh is white or pinkish; the gills are 
thin, crowded, white, then pink, later dark brown, distant from the stem, 
generally narrowed toward each end; the stem is long, bulbous, stuffed or 
hollew, whitish, sometimes yellowish below; the ring is membranaceous, 
sometimes with broad floccose patches on the under side. 
FIGURE 33.—Agaricus campestris, the common or cultivated mushroom. (Edible) 
AGARICUS CAMPESTRIS. COMMON OR CULTIVATED MUSHROOM. (EDIBLE) 
(Fig. 33) 
In this species the cap is rounded, convex, when expanded nearly plane, 
smooth, silky floccose or squamulose, white or light brown, squamules brown, 
margin incurved; the flesh is white, firm; the gills are white in the very 
young stage, then pink, soon becoming purplish brown, dark brown, or nearly 
black, free from the stem, rounded behind, subdeliquescent; the stem is white, 
subequal, smooth, or nearly so; the veil sometimes remains as fragments on 
the margin of cap; the ring is frail, sometimes soon disappearing. 
The cap is 1% to 4 inches broad; the stem is 2 to 8 inches long and 4 to 8 
lines thick. 
This is the most common and best known of all the edible mushrooms. It 
is a species of high commercial value, lending itself to a very successful and 
profitable artificial cultivation. It is cosmopolitan in its geographic distribu- 
tion, being as universally known abroad as in North America. It is cultivated 
in caves, cellars, and in especially constructed houses; but it also occurs 
abundantly in the wild state, appearing in pastures, grassy places, golf courses, 
and richly manured ground. The only danger in collecting it in the wild 
form is in mistaking an Amanita for an Agaricus; however, this danger may 
be obviated by waiting until the gills are decidedly pink before collecting the 
mushrooms. 
