inner
stratum.

The plants of the Nidulariaceae are very minute, tough, and widely
distributed. The species Cyathus, the "bird's-nest fungus," is quite
common in some localities, and is interesting because of its peculiar
form. The individual plant is very small, not more than two centimeters
high. It resembles an inverted bell, or a miniature wine-glass. A
delicate white membrane covers the top at first. This disappears as the
plant matures, revealing lentil-shaped bodies packed closely together
like eggs in a nest. These oval bodies are the peridiola containing the
spores. They are usually found upon rotten wood or sticks on the ground.
Sixty-five species are recorded, but none are edible.

The plants of the division Hypogaei or Hymenogastreae are subterranean in
habit, preferring a sandy soil. They are usually somewhat globose in
form, having a thick outer coat or peridium, though in some of the
genera the outer coat is very thin or obsolete. They are dingy in color.
In the young plants the interior substance somewhat resembles that of
the truffle, but is streaked and mottled. When old the gleba consists of
a dusty mass of threads and spores. They are known under various
appellations, such as "underground puff-balls," "false truffles," etc.

The Hypogaei are analogous to the Tuberacei, except that the spores are
not contained in asci as in the latter. Cooke says they appear to be the
link which unites the Basidiomycetes to the Ascomycetes by means of the
Tuberacei or genuine Truffles. In the young stage the basidia in the
Hypogaei are easily distinguished by the aid of the microscope.

In external features and habit of growth the species of Elaphomyces, a
genus of Tuberacei, closely resemble the Hypogaei, and in old age, when
the _asci_ have disappeared, it is difficult to distinguish the plants
of this genus from the Hypogaei.

The genus _Melanogaster_ contains an edible species, _M. variegatus_,
Tulasne, commonly known in Europe as the "Red Truffle" or "False
Truffle." _M. variegatus_ is usually gregarious and subterranean in
habit. The exterior is minutely granular, tawny yellow or reddish rust
color; the interior soft, bluish-black, streaked with yellow, the spore
mass in maturity becoming pubescent. The odor is pleasantly aromatic,
and the taste sweet. Under trees in woods. The variety _Broomeianus_
Berk. is paler in the marbling, which shows reddish instead of yellow
streaks. The pulpy mass is at first whi