- Hymenomycetes, in which the hymenium is free, mostly naked, or soon exposed. Example, "Common Meadow Mushroom."
- Gasteromycetes, in which the hymenium is enclosed in a second case or wrapper, called a peridium, which ruptures when mature, thus releasing the spores. Example, Common Puff Ball.
- Coniomycetes, in which the spores are naked, mostly terminal on inconspicuous threads, free or enclosed in a perithecium. Dust-like fungi. Example, Rust of Wheat.
- Hyphomycetes, in which the spores are naked on conspicuous threads, rarely compacted, Thread-like fungi. Example, Blue Mold.
Of these four subdivisions of the Sporifera, only the Hymenomycetes and the Gasteromycetes contain plants of the mushroom family, and these two together constitute the class known as the Basidiomycetes. The chief distinction of the Basidiomycetes is that the naked spores are borne on the summits of certain supporting bodies, termed basidia. These basides are swollen, club-shaped cells, surmounted by four minute tubes or spore-bearers, called sterigmata, each of which carries a spore. See Figs. 3 and 4, [Plate A].
These basides together with a series of elongated cells, termed paraphyses, packed closely together side by side, and intermixed with other sterile cells, called cystidia, constitute the spore-bearing surface or hymenium of the plant.
To the naked eye this hymenium appears simply as a very thin smooth membrane, but when a small portion of it is viewed through a microscope with high powers its complex structure is readily observed and can be carefully studied.
The Sporidiferous fungi are represented by the families Physomycetes and Ascomycetes. The first of these consists wholly of microscopic fungi.
Ascomycetes.—In the plants of this family the spores are not supported upon basidia, but instead are enclosed in minute sacs or asci formed from the fertile cells of a hymenium. In this connection it would be well to state that Saccardo does not recognize the divisions Sporifera and Sporidifera by those names.
They are nearly the equivalent of Basidiomycetes and Ascomycetes.
What Cooke names Physomycetes, Saccardo calls Phycomyceteæ, introducing it in his work between Gasteromyceteæ and Myxomyceteæ, which some mycologists consider somewhat out of place.
Saccardo calls its asci (sacs which contain the spores) sporangia. He does not regard them as genuine asci, but as corresponding more to the peridium of the Gasteromyceteæ and Myxomyceteæ.