troying fungi. The luminosity is often so bright that when brought
near a printed page in the dark, words can be read. Hawthorne "reported
the light from an improvised torch of mycelium infected wood, to have
carried him safely several miles through an otherwise impassable
forest." (Asa Gray, Bull. =7=: 7, 1900). The sulphur polyporus is said
sometimes to be phosphorescent. The _Clitocybe illudens_ (see Fig. 92)
has long been known to emit a strong phosphorescent light, and has been
called "Jack-my-lantern." This plant often occurs in great abundance. At
mountain hotels it is often brought in by day, and the guests at night,
discovering its luminosity, trace grotesque figures, or monograms, on
the ground by broken portions, which can be seen at a considerable
distance. _Lentinus stipticus_ in this country is also phosphorescent.
In Europe, the _Pleurotus olearius_ (very closely related to our
_Clitocybe illudens_) on dead olive trunks is one of the best known of
the phosphorescent species. Other phosphorescent species are, according
to Tulasne, _A. igneus_ from Amboyna, _A. noctileucus_ in Manila, and
_A. gardneri_ in Brazil.

The use of certain mushrooms in making intoxicant beverages is referred
to in Chapter XXII.

Since the artificial cultivation of mushrooms for food is becoming quite
an industry in this country with some, the following chapter is devoted
to a treatment of the subject. Mention may be made here, however, of the
attempts in parts of France to cultivate truffles, species of
subterranean fungi belonging to the ascomycetes (various species of the
genus _Tuber_). It had long been observed that truffles grow in regions
forested by certain trees, as the oak, beech, hornbeam, etc. Efforts
were made to increase the production of truffles by planting certain
regions to these trees. Especially in certain calcareous districts of
France (see Cooke, Fungi, etc., p. 260) young plantations of oak, beech,
or beech and fir, after the lapse of a few years, produced truffles. The
spores of the truffles are in the soil, and the mycelium seems to
maintain some symbiotic relation with the roots of the young trees,
which results in the increase in the production of the fruit bodies.
Dogs and pigs are employed in the collection of truffles from the
ground.

Comparatively few of the truffles, or other subterranean fungi, have
been found in America, owing probably to their subterranean habit, where
they are not readily obs