209 
by the Agency of Insects. 
firm skin or membrane, the external peridium ; (II) an inner 
thin membrane, the internal peridium ; (c) an intermediate 
much thicker layer of translucent, pale yellowish-brown gela- 
tinous material, the gelatinous layer. At the base there is a 
cup-shaped portion which supports the stem, and is continuous 
laterally by its margin with the peridial layers, and below with 
the mycelium. (2) A central medullary portion, composed of 
two very different structures : (a) the gleba, or spore-bearing 
part, which forms a hollow conical cap, lying within the inner 
peridium and surrounding the upper portion of the stem, to 
the apex of which it is firmly attached. Its outer surface 
bears the hymenium, and is honeycombed by a large number 
of irregular chambers or depressions, in which the mass of 
spores is lodged, (b) The stem, consisting of a cylinder whose 
walls at this stage are firm and solid-looking, and composed 
of a multitude of small, vertically compressed cavities filled 
with jelly. 
The volva is at first concealed beneath the surface of the 
soil, but towards maturity it breaks through the ground, and 
the exposed part gradually becomes conical and finally rup- 
tures, the stem rapidly lengthening and elevating the gleba in 
the air. These phenomena depend upon a peculiar mechanical 
change which occurs in the stem. The gelatinous contents of 
the flattened cavities disappear, and they become excessively 
dilated, the previously compact stem increasing threefold or 
fourfold in magnitude and becoming open and spongy, the dis- 
tension of the cavities being due to the secretion of air 1 . The 
protrusion and elevation of the gleba take place with great 
rapidity, and may be completed in from half-an-hour to two 
or three hours, the gleba attaining a height of from 5 or 6 to 
8 or 10 inches above the surface of the ground. The utility of 
this sudden elevation by the substitution of a rapid mechanical 
process for the slower process of simple growth will be evident 
in the sequel. 
At the time of emergence, and for a brief interval afterwards, 
1 De Bary, op. cit. p. 348. It struck me as being purely mechanical, like the 
expansion of a compressed sponge, air finding its way in by ruptures of the walls. 
