In Germany, the persons employed in gathering morells found that they always grew most abundantly in woods that had been burnt: and, with a view of promoting their increase, they were accustomed to set fire to the woods, until this practice was prohibited by the Government. Useful and palatable as these plants are, it has been ascertained that, if gathered after having been exposed for some days to wet weather, they are extremely pernicious. 294. _The TRUFFLE_ (Tuber cibarium) _is a globular, solid, and warty fungus, without root, which grows at the depth of four or five inches beneath the surface of the earth, and is from the size of a pea to that of a potatoe._ This, one of the best of the edible funguses, is chiefly found in hilly woods and pastures, which have a sandy or clayey bottom; and occurs on the downs of Wiltshire, Hampshire, and Kent. Truffles are generally discovered by means of dogs, which are taught to hunt for them by scent; and wherever they smell one of them, they bark, and scratch it up. In Italy they are hunted, in somewhat similar manner, by pigs. Truffles are either served at table roasted in a fresh state like potatoes, or they are cut into slices and dried, as an ingredient for sauces and soups. Those that are most delicious are internally of white colour, and have somewhat the odour of garlic. In England truffles seldom exceed the weight of four or five ounces; whilst on the Continent they are known to weigh as much as fifteen or sixteen ounces each. 295. _The PUFF-BALL_ (Lycoperdon bovista) _is a round kind of fungus, which is filled with a soft whitish flesh when young, and a fine brown powder when ripe._ The _powder_ of the puff-ball is sometimes used as a styptic, to prevent the bleeding of recent wounds. This powder is extremely subtile, and is very injurious to the eyes. Instances have occurred of persons who, having had it blown into their face, have thereby been deprived of their sight for a considerable time; and have also been affected with violent pain and inflammation. There is a curious experiment of taking a shilling from the bottom of a vessel of water, without wetting the hand. This is said to be effected by strewing a small quantity of the dust of the puff-ball on the surface; it so strongly repels the fluid as to form a covering for the fingers, and defend them from the contact of the water. The fumes of the puff-ball, when burnt, have a powerfully narcotic quality; and, on this account, they are sometimes used to take the combs from hives without destroying the bees. 296. _The COMMON MUSHROOM_ (Agaricus campestris) _is a fungus consisting of a white cylindrical stalk and a convex cover of white or brownish colour, which has beneath an irregular arrangement of gills, pinky when young, but afterwards of dark liver colour._ _When it first appears above ground the mushroom is smooth and nearly globular, and in this state it is called a_ button.