Page:Popular Science Monthly Volume 7.djvu/144

132 a pair of dark-colored spots near the top (see 2 and 3, Fig. 2), which mark the position of the future gills. A little later the cap begins to take shape, the gills develop, and a membrane may be seen stretching from the stem to the edge of the growing cap. As maturity approaches, this membrane is ruptured and forms a ring around the stem, as shown in Fig. 8. This membrane is called the veil or



volva. The parts to be borne in mind, then, are the mycelium or vegetative portion, and the stem, cap, gills, hymenium, ring, and volva, all of which belong properly to the reproduction of the plant, and all, except the hymenium, may be readily traced in Fig. 3.

If, when the mushroom is mature, you cut off the stem close to the gills, and place the cap, gills downward, upon a sheet of paper for a few hours, or all night, it will leave behind a likeness of itself in the shape of radiating lines that correspond to the spaces between the pairs of gills. These lines are formed by minute microscopic spores that have been thrown down in profusion from the hymenium, and in greatest number from the opposed surfaces of the gills. In making the experiment with this mushroom use white paper, but for light-spored species black paper should be taken. These little germinal bodies are cellular in structure, and of the extremest minuteness; thousands of them are required to form a body the size of a pin's-head. Their color is constant, and is used as a means of identification; but among the higher plants color is a character that cannot be thus relied upon. The spore is a simple cell, and the entire mushroom is cellular in composition. The delicate threads of the mycelium are formed of rows of cells placed end to end, and microscopic inspection of thin slices from the stem and cap show, that they also are composed of cells alone.