=HOW TO KNOW MUSHROOMS.=--One-sixth of one of the poisonous mushrooms has caused death. It is, therefore, impossible to exert too much care in selecting them for food. A novice would much better learn all the characteristics of edible and poisonous mushrooms in the field from an expert before attempting to gather them himself, and should not trust to book descriptions, except in the case of the few edible species described hereafter. It is not safe for a novice to gather the immature or button mushrooms, because it is much more difficult to determine their characteristics than those of the full grown. As reference books, the reader is advised to procure Bulletin No. 15 of the United States Department of Agriculture, entitled "Some Edible and Poisonous Fungi," by Dr. W. G. Farlow, which will be sent without charge on request by the Agricultural Department at Washington; "Studies of American Fungi," by Atkinson, and Miss Marshall's "Mushroom Book," all of which are fully illustrated, and will prove helpful to those interested in edible fungi. There are no single tests by which one can distinguish edible from poisonous fungi, such as taste, odor, the blackening of a silver spoon, etc., although contrary statements have been made. Even when the proper mushrooms have been eaten, ill effects, death itself, may follow if the mushrooms have been kept too long, have been insufficiently cooked, have been eaten in too large a quantity (especially by children), or if the consumer is the possessor of an unhappy idiosyncrasy toward mushrooms. No botanic distinction exists between toadstools and mushrooms; mushrooms may be regarded as edible toadstools. They are all, botanically speaking, edible or poisonous fungi. A description follows of the five kinds of fungi most commonly eaten, and the poisonous species which may be mistaken for them. =EDIBLE MUSHROOMS.=--=1. The Common Mushroom= (_Agaricus Campestris_).--The fungi called agarici are those which have gills, that is, little plates which look like knife blades on the under surface of the top of the mushroom, radiating outward from the stem like the spokes of a wheel. This is the species most frequently grown artificially, and sold in the markets. The top or cap of this mushroom is white, or of varying shades of brown, and measures from one and a half to three or even four inches in diameter. It is found in the latter part of August, in September, and in October, growing in clusters on pastures, fields, and lawns.