large order of pore fungi within the phylum Basidiomycota (kingdom Fungi). The 2,300 known species have conspicuous sporophores (fruiting bodies), sometimes mushroomlike, the spore-bearing layer (hymenium) appearing either tube-shaped, gill-like, rough, smooth, or convoluted. Many species are found on the ground or on decaying wood. Some species are edible; others cause diseases of trees.

The order includes the shelf, or bracket, fungi (Polyporaceae), which produce a shelf-like fruiting structure on many trees. They cause decay of birch and other hardwoods and of structural timbers (certain Poria species); conifer rot, heart rot, and root rot of rubber plants (Fomes); wood decay and root rot of cacao, coffee, rubber, and other trees (Ganoderma); and diseases of birch and conifers (Polyporus). The white undersurface of artist's fungus (Fomes applanatus), which darkens when cut, has been used for etching.

The inedible birch fungus Polyporus betulinus causes decay on birch trees in the northern United States. Dryad's saddle (P. squamosus) produces a fan- or saddle-shaped mushroom. It is light coloured with dark scales, has a strong odour, and grows on many deciduous trees. The edible hen of the woods (P. frondosus), which grows on old trees and stumps, produces a cluster of grayish mushrooms with two or three caps on a stalk; the undersides of the caps are porous. The sulfur mushroom, P. (Laetiporus) sulphureus, a common, shelf-like fungus that grows on dead wood, derives its name from its sulfur-yellow colour; only the younger portions of the fruiting body are edible.