tudded with basidia, each of which normally
terminates with four short, erect, delicate, thread-like processes,
each of which is surmounted by a spore. These spores are colourless or
coloured, and it is upon this fact that primary divisions in the genus
_Agaricus_ are based, inasmuch as colour in the spores appears to be a
permanent feature. In white-spored species the spores are white in all
the individuals, not mutable as the colour of the pileus, or the
corolla in phanerogamic plants. So also with the pink spored, rusty
spored, black spored, and others. This may serve to explain why
colour, which is so little relied upon in classification amongst the
higher plants, should be introduced as an element of classification in
one of the largest genera of fungi.

[Illustration: FIG. 45.--Spores of (_a_) _Agaricus mucidus_; (_b_)
_Agaricus vaginatus_; (_c_) _Agaricus pascuus_; (_d_) _Agaricus
nidorosus_; (_e_) _Agaricus campestris_. (Smith.)]

[Illustration: FIG. 46.--Spores of (_a_) _Lactarius blennius_; (_b_)
_Lactarius fuliginosus_; (_c_) _Lactarius quietus_. (Smith.)]

There are considerable differences in size and form amongst the spores
of the _Agaricini_, although at first globose; when mature they are
globose, oval, oblong, elliptic, fusiform, and either smooth or
tuberculated, often maintaining in the different genera or subgenera
one particular characteristic, or typical form. It is unnecessary here
to particularize all the modifications which the form and colour of
the spores undergo in different species, as this has already been
alluded to. The spores in the _Polyporei_, _Hydnei_, &c., are less
variable, of a similar character, as in all the _Hymenomycetes_,
except perhaps the _Tremellini_.

[Illustration: FIG. 46a.--(_a_) Spore of _Gomphidius viscidus;_ (_b_)
spore of _Coprinus micaceus_.]

[Illustration: FIG. 47.--Spores of (_a_) _Polyporus caesius_; (_b_)
_Boletus parasiticus_; (_c_) _Hydnum_.]

When an Agaric is mature, if the stem is cut off close to the gills,
and the pileus inverted, with the gills downwards on a sheet of black
paper (one of the pale-spored species is best for this purpose), and
left for a few hours, or all night, in that position, the paper will
be found imprinted in the morning with a likeness of the under side of
the pileus with its radiating gills, the spores having been thrown
down upon the paper in such profusion, from the hymenium, and in
greater numbers from the opposed surf