Xerocomus badius

Imleria badia, commonly known as the bay bolete, is an edible, pored mushroom found in Europe and North America, where it grows in coniferous or mixed woods on the ground or on decaying tree stumps, sometimes in prolific numbers. Both the common and scientific names refer to the bay- or chestnut-coloured cap, which is almost spherical in young specimens before broadening and flattening out to a diameter up to 15 cm (6 in). On the cap underside are small yellowish pores that turn dull blue-grey when bruised. The smooth, cylindrical stipe, measuring 4–9 cm (1.6–3.5 in) long by 1–2 cm (0.4–0.8 in) thick, is coloured like the cap, but paler. Some varieties have been described from eastern North America, differing from the main type in both macroscopic and microscopic morphology. First described scientifically by Elias Fries in 1818, the bay bolete was reclassified as Xerocomus badius in 1931, and it is still listed thus in several sources. Modern molecular phylogenetic studies show Xerocomus to be polyphyletic (not descended from a common ancestor), and the bay bolete is not particularly closely related to species in that genus. Often considered a poor relation of the cep (Boletus edulis), I. badia is nevertheless regarded as a choice edible mushroom by some authors, such as food expert Antonio Carluccio, and is sold in markets in Europe and central Mexico. Its mushrooms are less often infested by maggots than other boletes. Several European studies have demonstrated that the mushroom can bioaccumulate some trace metals from the soil, such as mercury, cobalt, and nickel. Additionally, the mushroom contains a pigment that concentrates radioactive caesium; specimens collected in Europe following the 1986 Chernobyl disaster contained several times more caesium-137 than those collected before the incident. The bay bolete was first named as Boletus castaneus ß badius (i.e. a subspecies of Boletus castaneus) by Elias Magnus Fries in 1818. Fries later renamed it as a variety of Boletus castaneus in 1828, before assigning it distinct species status in his 1832 work Elenchus Fungorum. The fungus has been transferred to several genera in its taxonomic history: Rostkovites by Petter Karsten in 1881; Viscipellis and Ixocomus by Lucien Quélet in 1886 and 1888, respectively; and Suillus by Otto Kuntze in 1898. In 1931, Edouard-Jean Gilbert reclassified it in the genus Xerocomus, and many sources still list it thus. Review of Xerocomus strongly suggested it was polyphyletic, and the genus was not accepted by some mycologists. The stickiness of its wet cap distinguishes the species from others classified in Xerocomus, and hence it was left in Boletus until Alfredo Vizzini placed it in its own genus in 2014. Genetic analysis published in 2013 shows that Imleria badia is related to B. pallidus and B. glabellus; the three species form a clade known informally as the badius clade within a larger group (informally called anaxoboletus) in the suborder Boletineae. Other clades within the group include the Tylopilus, porcini (= Boletus sensu stricto) and Strobilomyces clades, as well as two other groups composed of members of various genera including Xerocomus (the taxa designated as Xerocomus species in this clade are not Xerocomus species and require new taxonomic designations) and Xerocomellus. The species Boletus limatulus, originally published by Charles Christopher Frost in 1874, was later redescribed, 'with a slight tinge of irritation at the time, energy and gasoline spent', as a variety of I. badia by Wally Snell in 1945 (as Xerocomus badius var. limatulus). The taxon name comes from the Latin limatulus, 'rather polished' or 'refined'. Varieties glaber and macrostipitatus were described from Nova Scotia, Canada, in 1976. The starting date of fungal taxonomy had been set as January 1, 1821, to coincide with the date of the works of Swedish naturalist Elias Magnus Fries, the 'father of mycology'. Rolf Singer argued that setting the starting date earlier to Christiaan Persoon's 1801 publication of Synopsis would make a name change necessary, as he had originally given what is now known as Royoporus badius the combination Boletus badius Pers. and if the bay bolete was classified in the genus Boletus, the name would be unavailable and the names Boletus glutinosus Krombh. or B. spadiceus Krombh. (non Fr.) would have to be used instead. The species name is the Latin adjective badia, meaning 'chestnut brown'. The common name is likewise derived from the colour of the cap, likened to the coat of a bay horse. Alternate common names of a similar derivation include bay-brown bolete and bay-capped bolete, and it is known as bolet bai in French. It is also known as the false cep. Variety glaber was named for its smooth (Latin: glaber, 'without hairs') stipe, and macrostipitatus for its large (Latin: macro, 'large') stipe. Imleria badia fruit bodies have a chestnut to dark brown cap, which is almost spherical in young specimens before broadening and flattening out to a diameter of up to 15 cm (6 in). The cap margin is acute, and cap surface velvety when young and slightly sticky when wet or old. The cap cuticle is difficult to separate from the flesh underneath. On the cap undersurface, the pores are initially cream to pale yellow, but become greenish yellow or olive with age. They stain dull blue to bluish-grey when bruised or cut, and are easily removed from the flesh. The pores are initially circular, becoming more angular with age, and number about one or two per millimetre. The tubes are 0.8–1.5 cm (0.3–0.6 in) long, and are adnate to depressed around the area of attachment to the stipe. The flesh is mostly whitish or yellowish in some places; underneath the cap cuticle, it is brownish-pink or reddish brown. Initially firm, it begins to soften under the cap in older mushrooms. In some parts of the cap, such as the junction of the cap and the stipe, the flesh stains pale blue when injured or exposed to air, particularly in damp weather. This change is sometimes faint, and not persistent, as it eventually reverts to its original colour. The stipe is 4–9 cm (1.6–3.5 in) long by 1–2 cm (0.4–0.8 in) thick, and is similar in colour to the cap but paler, and sometimes with a rose-coloured tinge. Its surface has faint longitudinal ridges, a fine powdering, and fine reticulations (a net-like pattern of ridges) at the apex. It often has a whitish region at the base and the top, and white mycelium at the base. Unlike the bulbous stipe of many other boletes, the stipe of B. badius remains relatively slim and cylindrical. The flesh of the stipe gets tougher with age. Its smell has been described as fruity.