The method of life of the mushroom.—The mushroom, like all the [Pg 206] plants we have studied, thus consists of parts which perform one or other of two duties; that of feeding the plant, and that of continuing the race. In this case the food is supplied entirely by the underground mycelium; while the aërial part, consisting of stalk and cap, is concerned only with the work of scattering the spores. There is nothing corresponding to the leaf-green of the higher plants, and the mushroom is therefore unable to make use of the carbon dioxide of the air (p. 34) as the source of the carbonaceous food which is necessary for its life. Carbonaceous and mineral food alike are obtained from the soil by the underground mycelium. The plant is, in short, dependent upon carbonaceous food which has been previously built up by some other plant or animal, and can therefore grow only in soil containing decaying animal or vegetable matter. It would be quite unable to subsist upon the nutritive solution of salts which was seen (p. 29) to suffice (when supplemented by fresh air) for green plants. Fungi.—The mushroom belongs to a class of plants called the Fungi, all of which obtain their carbonaceous food ready-made from some other plant or animal, living or dead. For this reason many fungi are parasitic upon other living plants. Most of the diseases of crops and of forest trees are due to fungi. The moulds which destroy food are fungi, and the dry rot which ruins timber is caused by organisms of the same class. Toadstools.—The common meadow mushroom is a justly-esteemed article of food, but some other gilled fungi, which are intensely poisonous, bear a sufficiently close resemblance to mushrooms to render them dangerous. The student should therefore take every opportunity of examining these, and of comparing them with the edible mushroom in the manner described on p. 204. [Pg 207] 42. MOULDS. 1. The growth of moulds.—Damp three small slices of bread, and cover them with tumblers to prevent them from drying. Expose one slice to ordinary daylight; keep another in a dark place at about the same temperature; and submit the third to the direct rays of bright sunlight as much as possible. 2. White mould (Mucor).—In one or two days observe that the bread is covered with white fleecy threads. Some of these may grow to a height of an inch or more, and end in small black knobs which can be seen with the naked eye. The knobs contain spores. Examine the mould with the help of a lens. On which of the three pieces of bread is there most mould, and on which the least?