5:he anatomy of a musheoom. 
393 
chemists tell us, more than ninety per cent, of a mushroom is 
water, the walls of the cells must be delicate and communicate 
freely. We know that fungoid growth is proverbially rapid. 
To obtain a tolerably accurate idea of the structure of the tissue 
of an agaric, it is advisable to slice off with a razor a thin longi- 
tudinal section from the centre of the stem. Such a slice will 
exhibit delicate tubular cells, the general direction of which is 
lengthwise, with lateral branches, the whole interlacing so inti- 
mately that it is difficult to trace any individual thread very far 
in its course (fig. 8). Another slice, taken in a similar manner 
transversely across the stem, will exhibit a much more porous 
character from the cut ends of the tubes being presented to the 
eye, mixed with branches or lateral cells. It will be evident 
that the structure is less compact as it approaches the centre of 
the stem, which in many species is hollow. Another section, 
taken in either direction from the pileus, shows that although 
the same type of structure prevails the cell walls are even more 
delicate, and it is more difficult to trace the course of the cells. 
There is a less distinct longitudinal direction, less pronounced 
fibrous character, and greater uniformity in density. Finally, a 
section across the gills (as at fig. 13) will show with a lens their 
relation to the pileus, but if a slice be taken from the cut face 
of one of the gills, a delicate, but by no means impossible 
operation, the central portion will be seen to be precisely the 
same kind of structure as the pileus, and indeed to be an 
extension of the pileus in plates, with the special cells of the 
hymenium growing from them on each surface (fig. 14). It 
may be observed here, that in order to the successful manipula- 
tion of fungi of this class, so as to obtain thin and satisfactory 
sections, it is essential that the agaric should be freshly gathered 
and cut while still firm, and before it has parted with any of its 
water. This caution is especially necessary if the weather is 
mild and dry. 
A glance at the surface of the gills of almost any agaric will 
furnish the reason why they are nearly the same distance apart 
near the stem and near the circumference. Of course, if there 
were only one series of plates radiating from the stem, they 
would increase the distance between each other in proportion to 
their distance from the stem. This is obviated by a second, and 
a third, and even a fourth series, each shorter than the other, 
extending from the margin of the pileus inwards between the 
longer gills, so that the distance between gill and gill is nearly 
uniform over the whole of the under surface of the pileus. The 
arrangement is similar to the diagram given in the plate (fig. 4). 
The hymenium is the spore-bearing surface. In puff-balls 
the hymenium is enclosed within the peridium, or external en- 
velope, but in the mushroom it is exposed or naked, and spread 
