FUNGI. 313 
heat and moisture are applied. When the re- 
quisite conditions are present, and the mycelium 
begins to develop the reproductive tissue, there is 
formed at first a small round tubercle, in which 
the rudiments or miniature organs of the future 
plant may after a while be distinctly traced. In 
this infantile condition, the mushroom is covered 
completely with a fine silky veil or volva, which 
afterwards disappears. The tubercle rapidly in- 
creases, until at last it produces from its interior 
a long, thick fleshy stem or stipe, surmounted by 
a pileus, or round convex, concave, or flat cap, 
similar to that anciently worn by the Scottish 
peasantry. This is the organ of reproduction, 
equivalent to the thecze of mosses and the flowers 
of phanerogamous plants. This cap is covered 
with a veil or wrapper, which is ruptured at a 
certain stage, and retires to form an annulus or 
ring round the stem. When it is removed from 
the under side of the pileus, a number of vertical 
plates or gills is revealed of a pale pinkish-yellow 
or white colour, different from the rest of the plant, 
and radiating round the cap from a common centre. 
The whole of this apparatus is called the hymenium. 
Each of the gills, when examined under the micro- 
scope, is found to consist of a number of elongated 
cells called basidia, united together on both sides of 
a cellular stratum, and bearing at their summits 
