itiveness. Bruise it ever
so lightly, no matter where, on the cap, the stem, the tubes of the
undersurface: forthwith, the wounded part, originally a pure white, is
tinted a beautiful blue. Place this bolete in an atmosphere of carbonic
acid gas. We can now knock it, crush it, reduce it to pulp; and the
blue no longer shows. But extract a fragment from the crushed mass:
immediately, at the first contact with the air, the matter turns a most
glorious blue. It reminds us of a process employed in dyeing. The indigo
of commerce, steeped in water containing lime and sulfate of iron, or
copperas, is deprived of a part of its oxygen; it loses its color and
becomes soluble in water, as it was in the original indigo plant, before
the treatment which the plant underwent. A colorless liquid results.
Expose a drop of this liquid to the air. Straightway, oxidization works
upon the product: the indigo is reformed, insoluble and blue.

This is exactly what we see in the boletes that turn blue so readily.
Could they, in fact, contain soluble, colorless indigo? One would say
so, if certain properties did not give grounds for doubt. When subjected
to prolonged exposure to the air, the boletes that are apt to turn blue,
particularly the most remarkable, Boletus cyanescens, lose their color,
instead of retaining the deep blue which would be a sign of real indigo.
Be this as it may, these mushrooms contain a coloring principle which is
very liable to change under the influence of the air. Why should we not
regard it as the cause of the black tint when the maggots have liquefied
the boletes which turn blue? The others, those with the white flesh, the
edible bolete, for instance, do not assume this asphalty appearance once
they are liquefied by the grubs.

All the boletes that change to blue when broken have a bad reputation;
the books treat them as dangerous, or at least open to suspicion. The
name of Satanic awarded to one of them is an ample proof of our fears.
The caterpillar and the maggot are of another opinion: they greedily
devour what we hold in dread. Now here is a strange thing: those
passionate devotees of Boletus Satanas absolutely refuse certain
mushrooms which we find delightful eating, including the most celebrated
of all, the oronge, the imperial mushroom, which the Romans of the
empire, past masters in gluttony, called the food of the gods, cibus
deorum, the agaric of the Caesars, Agaricus caesareus. It is the most
elegant