The basidia of the Gasteromycetes, though resembling those of the Hymenomycetes, are more variable in form and the number of the spores not so constant. They perform the same functions and bear spicules, sometimes in pairs, sometimes quaternate, each spicule being surmounted by a spore. They dissolve away as the spores mature and can, therefore, only be observed in the very young stage of the plant. The spores of the Gasteromycetes are usually colored and, except in the subterranean species, globose. As seen through the microscope they have often a rough warty appearance, sometimes spinulose. Paraphyses may be present as aborted basidia, but cystidia are rarely distinguished. A characteristic of a large proportion of the plants is the drying up of the hymenial substance, so that the cavity of the receptacle becomes at length filled with a dusty mass composed of spores and delicate threads, the remains of the shriveled hyphæ.

The following table will serve to show the distinctive features of the four primary divisions of the Gasteromycetes:

The section Lycoperdaceæ contains upwards of 500 species or more than two-thirds of the whole number of recorded species of the Gasteromycetes. Lycoperdon, Bovista, and Geaster, its most conspicuous genera, are said to contain the largest number of well-known species. A few are edible.

The Phalloideæ include about 90 species. The plants are usually ill-smelling and unwholesome. Some are stipitate, others are latticed, etc. Some are conspicuous for their bright coloring. In the young stage they are enclosed in an egg-shaped volva having a gelatinous inner stratum.

The plants of the Nidulariaceæ 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 Hypogæi or Hymenogastreæ 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 Hypogæi 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 Hypogæi 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 Hypogæi, and in old age, when the asci have disappeared, it is difficult to distinguish the plants of this genus from the Hypogæi.

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 white, changing to a yellowish, smoky hue.