What You Should Know
Tylopilus felleus is an inedible bolete (but not poisonous) that has slightly to distinctly pink pores on the underside of the bun-shaped brown cap and a dark net on the thick stem are characteristic of this bolete. It is also distinguished by a very bitter taste.
This impressive, conifer-loving mushroom is widely distributed and common east of the Rocky Mountains wherever conifers occur naturally.
If you gather Boletus edulis or other boletes for eating, it is well worth getting to know how to distinguish the Bitter Bolete from other brown-capped species that have reticulated (netted) stems.
Accidentally including this imposter in a meal guarantees that it will be inedible to anyone who still has any taste buds.
In some countries, Tylopilus felleus is dried and used as a substitute for pepper.
Other names: Bitter Bolete, The Bitter Tylopilus, The Great Betrayer.
Tylopilus felleus Mushroom Identification
Mycorrhizal with conifers; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains.
5–13 cm; convex, becoming broadly convex or nearly flat in age; dry; bald and softly leathery; unpolished; sometimes becoming cracked; brown, fading to tan.
White at first, becoming pink; bruising pinkish-brown to brownish; pores circular, 1–2 per mm; tubes to 20 mm deep.
4–10 cm long; 1.5–4 cm thick; club-shaped; whitish to pale brownish above; pale brown to tan elsewhere; strongly reticulate with a wide-meshed, brown reticulum, at least over an upper third; basal mycelium white.
Thick; soft; white; unchanging when sliced.
Odor and Taste
Taste very bitter; odor not distinctive.
Ammonia negative to pale orange or pale pink on cap surface; negative on flesh. KOH orangish on cap surface; yellowish to orangish on flesh. Iron salts negative to greenish on cap surface; negative to pale gray on flesh; bluish-gray on tubes.
Spores 10–16 x 3–4 µm; narrowly fusiform to subfusiform; smooth; hyaline to yellowish in KOH. Hymenial cystidia 30–40 x 8–10 µm; widely fusiform; often developing a mucro; smooth; thin-walled; hyaline in KOH; occasionally with a refractive, golden, globular inclusion. Pileipellis a tangled cutis of cylindric elements 5–7.5 µm wide; golden yellow in KOH; terminal cells often erect, with rounded to subacute apices.
Tylopilus felleus Look-Alikes
Has a similar reticulate stipe but its pores do not flush coral pink.
Can have a similar-colored cap, but its yellow pores and slender stalk aid identification.
Found in hardwood forests of eastern North America, is similar in appearance to T. felleus, but has a purplish to the purple-brown cap. It is also inedible due to its bitter taste.
Another North American species, has a cap that is reddish-brown to chestnut-brown, with olive tones in youth. It has shorter spores than T. felleus, typically measuring 9–13 by 3–4.5 μm. In the field, it can be distinguished from the latter species by its mild to slightly bitter taste.
Found in the southeastern United States, has a lighter-colored cap that is smaller, up to 9 cm (3.5 in) in diameter.
Also can be confused with T. felleus, but have less reticulated stalks. The dimensions of the spores of the Australian species T. brevisporus range from 9.2 to 10.5 by 3.5 to 3.9 μm. T. neofelleus, limited in distribution to deciduous forests of China, New Guinea, Japan, and Taiwan, can be distinguished from T. felleus macroscopically by its vinaceous-brown cap and pinkish-brown to vinaceous stalk, and microscopically by its smaller spores (measuring 11–14 by 4–5 μm) and longer pleurocystidia (49–107 by 14–24 μm).
Tylopilus felleus Taxonomy and Etymology
The species was first described in the scientific literature as le bolet chicotin (Boletus felleus) by French mycologist Pierre Bulliard in 1788. As the large genus Boletus was carved up into smaller genera, Petter Karsten transferred it in 1881 to Tylopilus, a genus diagnosed by its pink spores and adnate tubes. T. felleus is the type species of Tylopilus, and the only member of the genus found in Europe. Synonyms include Boletus alutarius, described by Elias Magnus Fries in 1815 and later by Friedrich Wilhelm Gottlieb Rostkovius in 1844, and Paul Christoph Hennings's subsequent transfer of Fries's taxon into Tylopilus, T. alutarius.
Lucien Quélet placed the taxon in Dictyopus in 1886 and then Rhodoporus in 1888, but neither of these genera is recognized today, the former having been merged into Boletus and the latter into Tylopilus.
Genetic analysis published in 2013 shows that T. felleus and many (but not all) other members of Tylopilus form a Tylopilus clade within a larger group informally called anaxoboletus in the Boletineae. Other clades in the group include the porcini and Strobilomyces clades, as well as three other groups composed of members of various genera including Xerocomus, Xerocomellus and Boletus badius and relatives.
A variety described from the Great Lakes region, var. uliginosus, was recognized by Alexander H. Smith and Harry D. Thiers in 1971 based on its microscopic features, a distinction supported by Professor C.B. Wolfe of Pennsylvania State University. However, Index Fungorum does not consider this an independent taxon. Similarly, Boletus felleus var. minor, published originally by William Chambers Coker and A.H. Beers in 1943 (later transferred to Tylopilus by Albert Pilát and Aurel Dermek in 1974), has been folded into synonymy with T. felleus. Charles Horton Peck described Boletus felleus var. obesus in 1889, but no record of a type specimen exists. Although some records exist of T. felleus in Australia, their spores are of consistently smaller dimensions and this taxon has been classified as a separate species, T. brevisporus.
Tylopilus felleus derives its genus name from the Greek tylos "bump" and pilos "hat", and its specific name from the Latin fel meaning "bile" referring to its bitter taste, similar to bile.
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Photo 2 - Author: Dick Culbert from Gibsons, B.C., Canada (Creative Commons Attribution 2.0 Generic)
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