Russula brevipes

Russula brevipes is a species of mushroom commonly known as the short-stemmed russula or the stubby brittlegill. The fruit bodies are white and large, with convex to funnel-shaped caps measuring 7–30 cm (3–12 in) wide set atop a thick stipe up to 8 cm (3 in) long. The gills on the cap underside are closely spaced and sometimes have a faint bluish tint. The spores are roughly spherical and have a network-like surface dotted with warts. Forms of the mushroom that develop a bluish band at the top of the stipe are sometimes referred to as variety acrior.

Fruiting from summer to autumn, the mushrooms often develop under masses of leaves or conifer needles in a mycorrhizal association with trees from several genera, including fir, spruce, Douglas-fir, and hemlock. It is widespread in North America, and was reported from Pakistan in 2006. Although edible, the mushrooms have a bland or bitter flavor. They become more palatable once parasitized by the ascomycete fungus Hypomyces lactifluorum, a bright orange mold that covers the fruit body and transforms them into lobster mushrooms.

Russula brevipes was initially described by American mycologist Charles Horton Peck in 1890, from specimens collected in Quogue, New York. It is classified in the subsection Lactaroideae, a grouping of similar Russula species characterized by having whitish to pale yellow fruit bodies, compact and hard flesh, abundant lamellulae (short gills), and the absence of clamp connections. Other related Russula species with a similar range of spore ornamentation heights include Russula delica, R. romagnesiana, and R. pseudodelica.

There has been considerable confusion in the literature over the naming of Russula brevipes. Some early 20th-century American mycologists referred to it as Russula delica, although that fungus was described from Europe by Elias Fries with a description not accurately matching the North American counterparts. Fries's concept of R. delica included: a white fruit body that did not change color; a smooth, shiny cap; and thin, widely spaced gills. To add to the confusion, Rolf Singer and later Robert Kühner and Henri Romagnesi described other species they named Russula delica. Robert Shaffer summarized the taxonomic conundrum in 1964:

Russula delica is a species that everybody knows, so to speak, but the evidence indicates that R. delica sensu Fries (1838) is not R. delica sensu Singer (1938), which in turn is not R. delica sensu Kühner and Romagnesi (1953)… It is best to use R. brevipes for the North American collections which most authors but not Kühner and Romagnesi (1953), call R. delica. The name, R. brevipes, is attached to a type collection, has a reasonably explicit original description, and provides a stable point about which a species concept can be formed.

Shaffer defined the Russula brevipes varieties acrior and megaspora in 1964 from Californian specimens. The former is characterized by a greenish-blue band that forms at the top of the stipe, while the latter variety has large spores. The nomenclatural database Index Fungorum does not consider these varieties to have independent taxonomical significance. In a 2012 publication, mycologist Mike Davis and colleagues suggest that western North American Russula brevipes comprise a complex of at least four distinct species. According to MycoBank, the European species Russula chloroides is synonymous with R. brevipes, although Index Fungorum and other sources consider them distinct species.

The specific epithet brevipes is derived from the Latin words brevis "short" and pes "foot", hence "short-footed". Common names used to refer to the mushroom include short-stemmed russula, short-stalked white russula, and stubby brittlegill.

Fully grown, the cap can range from 7 to 30 cm (3 to 12 in) in diameter, whitish to dull-yellow, and is funnel-shaped with a central depression. The gills are narrow and thin, decurrent in attachment, nearly white when young but becoming pale yellow to buff with age, and sometimes forked near the stipe. The stipe is 3–8 cm long and 2.5–4 cm thick. It is initially white but develops yellowish-brownish discolorations with age. The mushroom sometimes develops a pale green band at the top of the stipe. The spore print is white to light cream.