394 
POPULAR SCIENCE REVIEW. 
over the gills. Those plates which grow side by side, radiating 
from the stem, on the under surface of the pileus, or cap, of a 
musliroom are covered on all sides with a delicate membrane 
upon which the reproductive organs are developed. This is the 
hymenium of the mushroom. If it were possible to remove this 
membrane in one entire piece and spread it out flat, it would 
cover a very large surface, for it is plaited or folded like a lady’s 
fan over the whole of the gill-plates or lamellse of the fungus. 
It is this surface which is at first creamy, then pink, and ulti- 
mately purplish-brown, the colour being communicated by the 
myriads of spores produced upon it. If the stem of a mushroom 
be cut off close to the gills, and the cap laid upon a sheet of 
white paper, with the gills downwards towards the paper, and 
left there for a few hours, when removed a number of dark 
radiating lines will be deposited on the paper, each line corre- 
sponding with one of the gills. These lines are made up of 
spores which have fallen from the hymenium ; if placed under 
a microscope their true character will be at once evident. 
Kemove a fragment of the thin membrane carefully from one of 
the gills and place it on a slip of glass, then examine it with 
the microscope. The whole surface will be seen studded with 
spores (fig. 7). The first peculiarity which will be observed is 
that these spores are almost uniformly ingroups of four together. 
The next feature to be observed is that each spore is borne 
upon a short slender stalk ; finally, that four of these stalks 
proceed from the apex of a thicker projection from the 
liymenium, such projection being therefore the bearer of 
four sterigmata, or little stalks, each surmounted by its spore. 
Take one of the gills and place it flat on a slip of glass, 
and then examine the free margin of the gill, so as to obtain a 
view of the projections from its surface sideways: and by this 
arrangement the observer will discover on the hymenium two 
kinds of projections — one, the 6asicZia, already alluded to, bear- 
ing spores; the other, cysiidia, larger projections, without spores. 
These two kinds of bodies which are produced on the hymenium 
of most, if not all, the agarics, demand a still closer investiga- 
tion. Before doing so it would be well to cut through the 
centre of one of the gills with a sharp razor, and from the cut 
surface to slice off a thin transverse section of the gill. By this 
process we shall discover that the cellular tissue of the pileus 
passes down the centre of the gills, that the cells are directed 
outwards towards the hymenium, that short cells intervene near 
tlie surface, and upon these compressed spherical cells the pro- 
jections, or h(LHulia and qintldia, are produced (fig. 14). There is 
no disjunction of the hymenium and the cellular structure of the 
hyineno|)horc, but the former is a continuation of the latter. 
To speak or write of the hymenium, therefore, as a distinct 
