Figure 17.—Agaricus rodmani. Entirely white, showing double veil or ring. (Natural size.) Copyright.
Variations in the surface characters of the cap and stem have led some to recognize several varieties. This is known as the common mushroom and is more widely known and collected for food than any other. It is also cultivated in mushroom houses, cellars, caves, abandoned mines, etc.
Agaricus (Psalliota) rodmani Pk. Edible.—Rodman's mushroom, Agaricus rodmani, grows in grassy places along streets of cities, either between the curbing and the walk, or between the curbing and the pavement. It is entirely white or whitish and sometimes tinged with yellowish at the center of the pileus. The plants are 4–8 cm. high, the cap 5–8 cm. broad and the stem 1–2 cm. in thickness.
Figure 18.—Agaricus arvensis, fairy ring.
The pileus is rounded, and then convex, very firm, compact and thick, with white flesh. The gills are crowded, first white, then pink, and in age blackish brown. The stem is very short, solid, nearly cylindrical, not bulbous. The annulus is quite characteristic, being very thick, with a short limb, and double, so that it often appears as two distinct rings on the middle or lower part of the stem as shown in Fig. [17]. This form of the annulus is probably due to the fact that the thick part of the margin of the pileus during the young stage rests between the lower and upper part of the annulus, i. e., the thick veil is attached both to the inner and outer surface of the margin of the cap, and when it is freed by the expansion of the pileus it remains as a double ring. It is eagerly sought and much relished by several persons at Ithaca familiar with its edible qualities.
The plant closely resembles A. campestris var., edulis, Vittad. (See Plate 54, Bresadola, I Funghi Mangerecci e Velenosi, 1899) and is probably the same.