—While it is quite impossible for a manual of this kind to give any directions by which a person, not an expert, may make certain distinctions between the edible and poisonous varieties of mushrooms, it is thought advisable to give a fair technical illustration of the two classes. The common mushroom, Agaricus campestris, is shown in the accompanying [Fig. 61],—three-fourths its natural size. The second specimen from the left is young and is in a state of development known as a button. The figure at the extreme left is a larger specimen, showing the slightly checked surface that sometimes occurs in this species. In fresh specimens the surface is white, but various shades of light brown, either checked or plain, are often found. The specimen at the right shows the gills on the lower surface of the cap. These gills in a newly expanded mushroom, fresh from the field, are of a beautiful delicate pale pink color, often with a touch of salmon. In the older samples the gills turn to a light brown and finally almost to a black color. This discoloration is chiefly due to the development of almost innumerable spores from which new plants are propagated. If the stem of a common mushroom be broken off and the cap be laid gills downward on a piece of white paper, the spores will drop off and after a few hours will appear as a brown dust. The usual diameter of full-grown specimens of this variety of mushroom is from 11⁄2 to 3 inches, though many smaller and many larger samples are found.
Fig. 61.—Common Mushroom, Agaricus campestris. Edible. (Three-fourths Natural Size.)—(F. V. Coville, Circular No. 13, Division of Botany, Department of Agriculture.)
This variety of mushroom is the principal one which is exposed upon the markets of Washington. They are especially abundant in the autumn after copious rains often succeeding the usual period of drought in that region. October is the banner month for this variety of mushroom. The mycelium from which the autumn mushroom grows is formed in the spring, and after the dry period of summer the little spheroid granules formed upon the mycelium are capable of absorbing the moisture of the warm autumnal rains and rapidly expand to the full-grown mushroom. After all the conditions of growth are fulfilled it usually requires only a single night for a button to push through the surface of the soil and expand its cap. Mushrooms are particularly obnoxious to the ravages of insects, and it is always advisable that they should be gathered and eaten immediately after they are formed. The insect larvæ attack the mature mushroom, travelling up through the stem into the cap, and decomposition rapidly follows.
Fig. 62.—Edible Mushrooms (Agaricus arvensis Schaeff.).—(F. V. Coville.)
It is easy to determine whether a mushroom is wormy or not by breaking off the stem close to the cap and observing if there are little holes through which the larvæ have passed upward into the cap. The common mushroom occurs most frequently on lawns and in pastures, and especially in neglected fields where weeds have been succeeded by a scant covering of grass. Sometimes during the spring and summer, as well as in the autumn, the common mushroom is found upon the market. These mushrooms usually are produced upon the garbage dumping grounds near the city. The garbage and refuse from the city furnish the manurial conditions required for a speedy development of the mushroom from the mycelium.
Fig. 63.—Shaggy Mushroom, Coprinus comatus. Edible. (Three-fourths Natural Size.)—(Coville, Circular 13, Division of Botany.)