The wiseacres tell us that they must have equal gills, must not have thin tops, must not turn yellow when sprinkled with salt, must not blacken a silver spoon, that we must not eat of those changing color when cut or broken, of those exuding milk, or those which are acrid, hot, or bitter, and give many other specifics for determining the good from the bad. These tests are all worse than worthless, for if confidence is placed in them they will not only lead us away from esculent and excellent varieties but directly into eating venomous ones. There are whole genera of fungi which are innocuous; but in the Family of Agaricaceæ, where the greatest variety of the edible and poisonous species are found, it is necessary to master one by one the details of their construction and learn to distinguish their differences as one does those of the many kinds of roses, or pinks, or hundreds of bright-faced pansies, and in the mastery of them lies the only charm that will safely guide. Carefully remove the first toadstool found from whatever it is growing upon, and with it a portion of that from which it springs. If it is the earth a curious white network is discernible, fine as the delicate spinning of the spider, spreading its meshes throughout the mass. It will often remind of miniature vines climbing over miniature lattices. This is the mycelium from which the toadstool grew. In many instances it penetrates the earth to a considerable depth, and takes possession of large territory. It is often seen as the gardener turns up the soil or its fertilizer, and is perhaps taken for a mold. If the specimen is gathered from mat of wood leaves, the same white vine is observable slipping in between its layers. If taken from a tree, the decaying wood is traversed by it. From wherever a toadstool is plucked, it is removed from its mycelium. This mycelium is but a thread-like mass of simple cells joined together at their ends and interlacing in a way a thousand-fold more intricate than a Chinese puzzle. Nothing in its structure indicates what its special product will be. The fungus which is plucked from it is in all its parts simply a mass of these threads—cells strung together, interlacing and ramifying. When the season favors, the mycelium—which has, winter and summer and from year to year, lived its hidden life, or has sprung from a germinating spore—develops a number of its cells in a minute knob, small as a pin head. At this point the cells make special growth efforts to bring themselves within the favoring influences of heat and moisture; this tiny knob labors within itself, producing cell after cell, which takes shape and function for the future toadstool. As it rapidly enlarges it pushes its way toward the surface of the ground, becomes more or less egg-shaped in this stage of its growth, and if cut in half longitudinally and examined, it will display what it is going to be when it grows up.