en gained.
This blue colour is so universally confined to dangerous species that
it is given as a caution that all species which exhibit a blue colour
when cut or bruised, should on no account be eaten. The degree of
intensity varies considerably according to the condition of the
species. For example, _Boletus caerulescens_ is sometimes only very
slightly, if at all, tinged with blue when cut, though, as the name
implies, the peculiar phenomenon is generally highly developed. It
cannot be said that this change of colour has as yet been fully
investigated. One writer some time since suggested, if he did not
affirm, that the colour was due to the presence of aniline, others
have contented themselves with the affirmation that it was a rapid
oxidization and chemical change, consequent upon exposure of the
surfaces to the air. Archdeacon Robinson examined this phenomenon in
different gases, and arrived at the conclusion that the change depends
on an alteration of molecular arrangement.[I]

One of the best of the edible species of _Lactarius_, known as
_Lactarius deliciosus_, changes, wherever cut or bruised, to a dull
livid green. This fungus is filled with an orange milky fluid, which
becomes green on exposure to the air, and it is consequently the juice
which oxidizes on exposure. Some varieties more than others of the
cultivated mushroom become brownish on being cut, and a similar change
we have observed, though not recorded, in other species.

The presence of a milky juice in certain fungi has been alluded to.
This is by no means confined to the genus _Lactarius_, in which such
juice is universal, sometimes white, sometimes yellow, and sometimes
colourless. In Agarics, especially in the subgenus _Mycena_, the gills
and stem are replete with a milky juice. Also in some species of
_Peziza_, as for instance in _Peziza succosa_, B., sometimes found
growing on the ground in gardens, and in _Peziza saniosa_, Schrad.,
also a terrestrial species, the same phenomenon occurs. To this might
be added such species as _Stereum spadiceum_, Fr., and _Stereum
sanguinolentum_, Fr., both of which become discoloured and bleeding
when bruised, while _Corticium lactescens_ distils a watery milk.

Fungi in general have not a good repute for pleasant odours, and yet
it must be conceded that they are not by any means devoid of odour,
sometimes peculiar, often strong, and occasionally very offensive.
There is a peculiar odour common to a great