392 
POPULAR SCIENCE REVIEW. 
A longitudinal section at this stage shows that the gills are being 
developed, that the pileus is assuming its cap-like form, that 
the membrane stretching from the stem to the edge of the 
young pileus is separating from the edge of the gills, and forming 
a veil, which, in course of time, will fall away and leave the gills 
exposed (fig. 3). When, therefore, the mushroom attains almost 
to its maturity, the pileus expands, and in this act the veil, or 
membrane, extending from the edge of the pileus to the stem, is 
torn away from the margin of the cap, and remains for a time 
like a collar round the stem (fig. 6 c). Fragments of the veil 
often remain attached to the margin of the pileus, and the collar 
adherent to the stem falls back, and thenceforth is known as 
the annulus, or ring. We have in this stage the fully developed 
hymenophore, the stem, with its ring, supporting an expanded 
cap, or pileus, with gills on the under surface bearing the 
hymenium (to be described hereafter). A longitudinal section 
cut through the pileus and down the stem (fig. 6) gives the best 
notion of the arrangement of the parts and their relation to the 
whole. By this means it will be seen that the pileus {d) is con- 
tinuous with the stem (6), that the substance of the pileus de- 
scends into the gills, and that relatively the substance of the 
stem is more fibrous than that of the pileus. More special details 
of the cell structure must be made out with the microscope. 
There are two or three features of systematic importance which 
may be observed by the naked eye, and these relate to the 
distinctions between the “ mushroom ” and other agarics. 
The stem of the mushroom is not hollow or tubular as in 
some specias, but continues to the centre, although less firm 
than near the circumference. When cut the surface immedi- 
ately changes colour, and becomes brownish by a kind of oxi- 
dation caused by exposure to the atmosphere. In a transverse 
section of the stem this coloration does not take place in the 
centre, but a portion resembling the pith in the stems of some 
flowering plants remains white (fig. 1 0). The ring is very distinct, 
surrounding the stem, a little above the middle, like a collar. In 
some agarics the ring is very fugacious, or absent altogether. 
'J'he cap or pileus is thick and fleshy, at first convex, and ulti- 
mately Ijccoming almost flat in the centre, but not depressed. 
The gills are broad, widest near the middle and attenuated 
towards each end (fig. 6 c). Their inner extremity reaches, but 
is not attached to the stem. At first they are flesh-coloured and 
finally ]>rown. All these features are of importance in deter- 
mining the species to wliich an agaric belongs. The mishaps 
wliich accompany the eating of fungi, when they occur, may be 
tnveed to a negligence in regarding these particulars, especially 
the presence of the ring and the colour of the gills. 
Tlie wliole substance of tlie mushroom is cellular. If, as 
