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a class of higher fungi having special reproductive organs, or basidia. The typical mature basidium has four single-cell spores (basidiospores) located in special excrescences, or sterigmata. During germination each basid-iospore puts forth a septate primary (haploid mycelium) or a spawn. Thus, in most basidiomycetes a merging of cells of the same or different (heterothallic) spawns takes place. The diploid mycelium usually develops sexual bodies. (Rust fungi and smut fungi are spore bearing.) Later, meiosis occurs in the basidia (for smut and rust fungi, in the spores); this ends with the formation of usually four nuclei, which migrate to the now-developed basidiospores.
The class Basidiomycetes includes more than 15,000 species. Many of them are edible (for example, birch mushroom, cepe, and peppery lactarius), some are poisonous (fly agaric and death cup), some cause wood rot, and some destroy many agricultural crops. The classification of basidiomycetes is based upon the structural peculiarities of its sexual organs and spore bearing. Basidiomycetes are usually divided into two subclasses: Holobasidiomycetes, which has a single-cell basidium called the holobasidium, and Phragmobasidiomycetes, which has either a four-celled basidium, the so-called phragmobasidium, or a single-cell spheroid, pear-shaped, or elongated dichotomously bifurcate basidium. The subclass Holobasidiomycetes is divided into the following orders: (1) Exobasidiales, without sexual organs and basidia developing on the spawn under the epidermis of the feeding plant (parasites); (2) Aphyl-lophorales; (3) Agaricales; and (4) Gasteromycetales. The subclass Phragmobasidiomycetes is divided into the following orders: (1) Ustilaginales, (2) Uredinales, (3) Au-riculariales, (4) Tremellales, (5) Dacryomycetales, and (6) Tulasnellales. The sexual organs of the latter four orders are mostly of a jelly-like consistency. The phragmobasidia which grow on them are divided into four cells either crosswise, as in the Auriculariales, or lengthwise, as in the Tremellales; or they are single-cell basidia, dichotomously bifurcate, as in the Dacryomycetales, or spherical or pear-shaped, as in the Tulasnellales.
REFERENCESKursanov, L. I. Mikologiia, 2nd ed. Moscow, 1940.
Bondartsev, A. S. Trutovye griby Evropeiskoi chasti SSSR i Kav-kaza. Moscow-Leningrad, 1953.
T. L. NIKOLAEVA