Black velvet bolete

Appearance

The shape of the cap is initially convex before later becoming broadly convex to eventually flattened in maturity; the diameter of the cap is typically between 3 and 15 cm . The cap surface is dry, with a velvet-like texture, although in age it can become ''rimose'' . The cap color is initially black to dark grayish brown; young specimens can have a whitish bloom on the surface. Fruit bodies, especially young specimens, tend to be free of maggots and other insect larvae. As the mushroom matures, the bloom disappears and the color fades to become grayish to grayish brown. The cap flesh is whitish, but after it is cut or injured, it will stain pink to reddish gray, and eventually turn black.

Spores are produced in basidia that are arranged in a vertically arranged layer of minute tubes on the underside of the cap that create a surface of pores. This surface is whitish when young before turning dull pink or flesh-colored in maturity. When bruised, the pore surface initially stains reddish and slowly turns black. The shape of the pores is angular to irregular, and they are small, with roughly two pores per millimeter. The tubes are 5–10 mm deep, and usually sunken around the area of attachment to the stem. The stem is 4–10 cm long by 2–4 cm thick, and is equal in width throughout its length, slightly thicker towards the base, or somewhat thicker in the middle. It is the same color as the cap, or paler. The surface texture of the stem is usually smooth, although some specimens may be slightly reticulated near the top. The spore print can range from pinkish to a deep flesh color.

The spores are oval to ellipsoid in shape, smooth, hyaline , and measure 7–11 by 3.5–5 μm. The basidia are club-shaped, four-spored, and measure 15–24 by 6–7.5 μm. Pleurocystidia are irregularly club-shaped, with dimensions of 20–36 by 7–10 μm, while cheilocystidia are club-shaped, rare, occur singly, and measure 18–32 by 7–9 μm. Although rare, there are also caulocystidia that are arranged in groups, and which measure individually 24–30 by 6–9 μm. Clamp connections are absent from the hyphae of ''T. alboater''.

''Tylopilus alboater'' is an edible mushroom with a pleasant odor and a mild taste. It is considered one of the best of the edible ''Tylopilus''—a genus that is usually associated with bitter-tasting, unpalatable species. Frying slices of the mushroom brings out a "delicate, earthy, nutty flavor"; longer frying times make the cap "pleasantly crisp". The mushrooms can be used in mushroom dying.

Naming

The species was first described in 1822 as ''Boletus alboater'' by Lewis David de Schweinitz from specimens he collected in North Carolina. Elias Magnus Fries sanctioned this name in his 1821 ''Systema Mycologicum''. The species was one of several ''Boletus'' species that Otto Kuntze transferred to ''Suillus'' in his 1898 ''Revisio Generum Plantarum''. American mycologist William Alphonso Murrill transferred it to the genus ''Tylopilus'' in 1909. In 1931, French mycologist Jean-Edouard Gilbert transferred the species to his newly created genus ''Porphyrellus'', but this name has since been subsumed into ''Tylopilus''.

In 1875, Charles Horton Peck described ''Boletus nigrellus'' from specimens he collected in Sand Lake, New York. Murrill reduced this name to synonymy with ''T. alboater'' in 1916, and noted that Peck's description was made from young material obtained "before the white tubes had been colored by mature spores". Several later authorities have treated Peck's species as a synonym of ''Tylopilus alboater''; this synonymy, however, is not indicated by either of the taxonomic authorities Index Fungorum or MycoBank.

The specific epithet ''alboater'' means "white and black". It is commonly known as the "black velvet bolete"; Murrill called it the "blackish bolete".Some ''Tylopilus'' species have a superficial resemblance to ''T. alboater'' and might be confused with it, including ''T. atronicotianus'', ''T. atratus'', and ''T. griseocarneus''. ''T. atratus'' produces smaller fruit bodies with caps up to 9 cm in diameter, and its whitish flesh directly stains black without any intermediate reddish phase when injured. It is known from only from western New York state. The "false black velvet bolete", ''T. atronicotianus'', has a brownish cap that lacks the velvety texture of ''T. alboater'', and has stems that are minutely velvety and almost black near the base. ''T. griseocarneus'', found in the Atlantic and Gulf Coastal Plains of North America, is readily distinguished from ''T. alboater'' by the strong orange to red discoloration that results when cutting or damaging the flesh of a fresh specimen. Furthermore, ''T. griseocarneus'' lacks the whitish bloom present on young caps of ''T. alboater'', and typically has a more prominently reticulated stem. Specimens of ''T. alboater'' that are paler than usual can be confused with ''T. ferrugineus'', but the latter has yellow cystidia when mounted in KOH, while the cystidia of the former are brownish yellow under similar conditions.

Distribution

''Tylopilus alboater'' is a mycorrhizal species, and its fruit bodies grow on the ground solitarily, scattered, or in groups under deciduous trees, particularly oak. Fruiting occurs in deciduous, coniferous, and mixed forests. Its dark color makes it difficult to notice in the field.

In North America, the mushroom is widely distributed east of the Rocky Mountains. The distribution ranges from Quebec in Canada, south to the New England states down to Florida, extending west to Missouri, Michigan, and Texas. It is also found in Mexico. In Asia, it has been recorded from China , Japan, Taiwan, and Thailand.

Habitat

''Tylopilus alboater'' is a mycorrhizal species, and its fruit bodies grow on the ground solitarily, scattered, or in groups under deciduous trees, particularly oak. Fruiting occurs in deciduous, coniferous, and mixed forests. Its dark color makes it difficult to notice in the field.

In North America, the mushroom is widely distributed east of the Rocky Mountains. The distribution ranges from Quebec in Canada, south to the New England states down to Florida, extending west to Missouri, Michigan, and Texas. It is also found in Mexico. In Asia, it has been recorded from China , Japan, Taiwan, and Thailand.