Hymenomycetes

(mycology) A group of the Homobasidiomycetidae including forms such as mushrooms and pore fungi in which basidia are formed in an exposed layer (hymenium) and basidiospores are borne asymmetrically on slender stalks.

An artificial class of fungi in the phylum Basidiomycota. It was traditionally divided into two subclasses: Holobasidiomycetidae, delimited by nonseptate basidia and the absence of a yeast phase; and Phragmobasidiomycetidae, frequently with septate basidia and often forming a yeast phase. A typical hymenomycete produces a fruit body or basidiome with spore-bearing basidia organized in a membranelike layer called the hymenium. The shape of the hymenium varies from lamellate (gilled as in mushrooms), poroid (as in conk or bracket fungi), toothed (in hedge hog fungi), coralloid (coral fungi), labyrinthoid (daedaleoid fungi), wrinkled (merulioid fungi), or smooth to diffuse (corticioid fungi). Exceptional hymenomycetes may be aquatic, lack a mycelial phase, or lack a fruit body.

Antibiotics have been isolated from many species. Commercially grown edible species include the button mushroom (Agaricus bisporus), Shiitake (Lentinula edodes), Paddy Straw mushroom (Volvariella volvacea), and Wood Ear (Auricularia polytricha). Wild harvested species include the Matsutake (Tricholoma matsutake and T. magnivelare), chanterelles (Cantharellus cibarius and allies), and the King Bolete (Boletus edulis).

Most genera are either saprophytic (for example, Agaricus and Polyporus), or mycorrhizal with trees (Albatrellus, Cortinarius, Ramaria, and Thelephora). Others are parasites. Heterobasidion causes destructive tree diseases; Rhizoctonia and Typhula (snow molds) cause field crop losses; Mycena citricolor blights coffee leaves; and Exobasidium, an obligate plant pathogen, induces the formation of galls and leaf curls. Other notable pathogens include Hohenbuehelia and Pleurotus, which capture nematodes; Serpula, a major dry-rot agent; Dictyonema, a basidiolichen; and Septobasidium, which harnesses living scale insects. See also Basidiomycota; Eumycota; Fungi; Plant pathology.