Agaricus oreades, Withering, Brit. Pl., vol. iv.; A. pratensis, J. Sowerby, Eng. Fungi J. Sowerby, Jun. The Mushroom and Champignon illustrated; A. Pseudo-Mousseron, Bulliard; Fairy Ring Agaric; Scotch Bonnets.—This indigenous plant occurs in pastures, and is one of several fungi which grow in circles forming what have been termed Fairy-rings. It is commonly sold in the shops for use at table, and is liable to be mistaken for several other species of Agaricus, viz.: A. dealbatus, dryophilus, semiglobatus, and foenisecii. Of these, A. dealbatus is the only one which, like the true champignon, forms "fairy-rings."
The fungus varies in colour from a pale to a deep buff or nankeen colour. The stem is 1 or 2 inches high, and 2 or 3 lines thick, round, solid, often slightly twisted, readily splitting longitudinally into silky fibres, and is of the same colour as the gills. The pileus or cap is from 1/2 to 1 inch in diameter, irregularly round, convex, most elevated in the centre, tough and coriaceous. The gills free, distant, waved at the edges, often lacerated, paler than the pileus. "If the pileus be cut through (Fig 193, b) the gills will not be found to separate from it, but the fleshy part runs down the middle of each gill, which is covered by the continuation of the same buff-coloured coat that lines the under surface of the pileus between the gills—a structure widely different from the poisonous one [Ag. semi-globatus]" [Sowerby, Jr., The Mushroom and Champignon Illustrated.]. Taste and odour agreeable.
A. dealbatus, Sowerby (Fig. 193, c d e) is distinguished from the champignon by the margin of the pileus being at first rolled inwards, by its very fine dingy whitish gills, by its becoming gray-brown in zones when soaked in water, and by its disagreeable odour. This species, according to Mrs. Hussey, resembles the champignon more than any other; and like it also grows in fairy-rings.
A. semi-globatus, Batsch. (Fig. 193, i k); the A. virosus of Sowerby is distinguished from the champignon by its dark-coloured gills, its hollow stem, and shining glutinous pileus. When young, this species has an annulus or ring, but this commonly disappears when the plant has attained its full size.
A. foenisecii, Persoon (Fig. 193, l m), is distinguished from the champignon by its dark-coloured gills, its hollow stem, and its umber-purple spores.
A. dryophilus, Bulliard (Fig. 193, f g h), is distinguished from the champignon by its fine close gills, its hollow stem, and its reddened swollen base.
Like the Agaricus campestris, or mushroom, the A. oreades, or Champignon, is used at table on account of its savory qualities, and not for its nutritive power, which is probably very slight.
The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1853.