Part 183. The spore-base fungi (Class Basidiomycetes) are well represented by the mushrooms, although very many widely diverse forms are included among its other members. The common field mushroom (Figs. 119, 330) vegetates by subterranean hyphae feeding upon decaying organic matter in the soil. From this mycelium arise, finally, compact masses of hyphae forming fruit-bodies which soon become differentiated into a vertical stalk and a horizontally expanded cap. From the under side of the cap hang numerous thin plates, called "gills," which radiate from the stalk to the margin of the cap. These gills (Fig. 331) bear the spore-producing layer which consists of swollen cell-tips beyond which project club-shaped bodies developing horns, each tipped with a spore. These club-shaped spore-bases are called basidia.1

1 Ba-sid'i-um - Gr. basis, base.

Fig. 330. Field Mushroom (see also Fig. 119). A, mycelium (m) producing young fruit bodies, 1/1. I, a very young fruit body cut vertically to show its relation to the mycelium (m). II, same, a little older, showing the beginnings of gills (1). Ill, IV, V, later stages in which appear the stalk (st), the cap (h) and the veil (v) protecting the gills till they are ripe.

Fig. 330.-Field Mushroom (see also Fig. 119). A, mycelium (m) producing young fruit-bodies, 1/1. I, a very young fruit-body cut vertically to show its relation to the mycelium (m). II, same, a little older, showing the beginnings of gills (1). Ill, IV, V, later stages in which appear the stalk (st), the cap (h) and the veil (v) protecting the gills till they are ripe. (Sachs.)

Fig. 331. Field Mushroom. A, vertical section through part of cap (h) at right angles to gills (1), slightly enlarged. B, cross section through a gill, showing the mass of hyphae (t) continuous with that of the cap, the spore bearing layer or hymenium (hy), and the layer (sh) from which it developes. C, a part of B (280/1), showing the development of dust spores (s' s

Fig. 331.-Field Mushroom. A, vertical section through part of cap (h) at right angles to gills (1), slightly enlarged. B, cross-section through a gill, showing the mass of hyphae (t) continuous with that of the cap, the spore-bearing layer or hymenium (hy), and the layer (sh) from which it developes. C, a part of B (280/1), showing the development of dust-spores (s'-s"") upon the tip of projections from swollen hyphatips or basidia, and other swollen tips (paraphyses, q) which form a large part of the hymenium but do not produce spores. (Sachs.)

The possession of basidia characterizes the class, in which, moreover, sporangia are, entirely lacking and scarcely a trace of any sexual organ has been found.