The A. campester is known the world over as the common mushroom. It is cosmopolitan, appearing in pastures and rich places from spring and until long after severe frosts. It is the sweet morsel of gourmets. Indirectly it has done more damage than the assembled viciousness of all other toadstools. It is by mistaking the young button forms of the deadly Amanita for the button forms of the common mushroom that most cases of fatal toadstool poisoning are brought about. It is, also, usually the persons who think they know the mushroom, and can not be deceived, that get poisoned. If two rules are observed danger can be avoided. (1) Never eat a fungus gathered in the woods believing it to be the mushroom. The typical A. campester does not grow in the woods; species of Agaricus somewhat resembling it do. (2) Look at the gills; those of the mushroom are at first a light-pink which rapidly, as the plant matures, darken to a dark-brown, purplish-brown, or purplish-black. This is due to the ripening of the spores. Those of the Amanita are constantly white. Pages could be written upon the mushroom and its culture, and recipes for the cooking of it would fill a volume. One important thing is omitted from them all—it is culinary heresy to peel a mushroom. Much of the flavor lies in the skin, as it does in that of apples, apricots, peaches, grapes, cherries and other fruits. The mushroom should be wiped with a coarse flannel or towel until the skin is clean. See chapter on cooking, etc. Lafayette B. Mendel, in American Journal of Physiology, March, 1898, gives the following analysis of A. campester: Two varieties of the common mushroom were collected in New Haven. Fifteen specimens of one variety weighed 1½ ounce, an average weight of 43 grains each. The analysis gave: _a._ _b._ Water 87.88% 92.20% Total solids 12.12 7.80 Total nitrogen in dry 4.42 4.92 substance Ash in dry substance 11.66 17.18 =A. comp´tulus= Fr.—_comptus_, gaily adorned. =Pileus= 1–1½ in. broad, _yellowish-white_, slightly fleshy, convex then plane, obtuse, _adpressedly fibrilloso-silky_, becoming even. =Flesh= thin, soft, of the same color as the pileus. =Stem= 2 in. long, 2–3 lines thick, _hollow_, stuffed with floccules when young, _somewhat attenuated_, even, smooth, white, becoming somewhat light yellow. =Ring= medial, torn, _fugacious_, of the same color. =Gills= rounded-free behind, crowded, soft, broader in front, _flesh-color_ then _rose_, not dingy-flesh-color except when old. Closely allied to A. campestris, but constantly distinct in its more beautifully colored gills. _Fries._ Cultivated ground. Menands. August. _Peck_, Rep. 41.