Tylopilus rubrobrunneus

[ Basidiomycetes > Boletales > Boletaceae > Tylopilus . . . ]

by Michael Kuo

This beautiful but very bitter tasting eastern mushroom is very common in some years--and seemingly absent in others. Because young specimens of Tylopilus rubrobrunneus have a purplish cap, the species is easily confused with Tylopilus plumbeoviolaceus and Tylopilus violatinctus, but both of those species have purple stems when young, while the stem of Tylopilus rubrobrunneus is never purple.

In my area (central Illinois), at least four species of Tylopilus can look very similar, especially at maturity, when their caps have faded to tan. Distinguishing these mushrooms in the field requires close observation of three details:

• Taste. Tylopilus rubrobrunneus and Tylopilus felleus are quite bitter, while Tylopilus indecisus and Tylopilus badiceps are mild.

• Pore surface. Tylopilus rubrobrunneus has a pore surface that bruises pinkish, while the pore surfaces of Tylopilus felleus, Tylopilus indecisus and Tylopilus badiceps bruise brown.

• Stem. Tylopilus felleus is strongly reticulate; the other three species are not reticulate, or merely slightly so at the apex of the stem. The stem of Tylopilus rubrobrunneus becomes relatively long, with a somewhat swollen bottom half, and usually demonstrates olive shades in places by maturity. The stems of the other three species do not typically become long and swollen, and do not develop olive colors.

Description:

Ecology: Mycorrhizal with hardwoods (especially oaks and Beech) but also in mixed woods or under Eastern Hemlock; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains, and recorded from Texas.

Cap: 8-30 cm; convex, becoming broadly convex or nearly flat in age; dry; smooth or finely felty; sometimes becoming cracked; the margin inrolled at first; dark purple or purple-brown when young, quickly becoming purplish brown, brown, cinnamon, or tan.

Pore Surface: Whitish becoming pinkish and finally dingy brown; bruising brownish; pores circular, 1-2 per mm; tubes to 20 mm.

Stem: 6-20 cm long; 1-5 cm thick; more or less equal when young, but usually enlarging toward the base with maturity; whitish to brownish or purplish; typically with olive-brown stains or bruising this color; smooth, or sometimes very finely reticulate near the apex.

Flesh: Thick and white; sometimes discoloring olive around worm holes.

Odor and Taste: Taste very bitter; odor not distinctive.

Chemical Reactions: Ammonia negative on cap surface; negative on flesh. KOH rusty orange on cap surface; negative on flesh. Iron salts negative on cap surface; negative to pinkish on flesh.

Spore Print: Dull pinkish to reddish brown.

Microscopic Features: Spores 10-14 x 3-4.5 µ; nearly oblong, or spindle-shaped; smooth. Pileipellis of mostly erect, cylindric elements with rounded or subclavate (but not cystidium-like) apices.

REFERENCES: Mazzer & Smith, 1976. (Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Both, 1993; Horn, Kay & Abel, 1993; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Binion et al., 2008.) Herb. Kuo 07079502, 09010204, 07020707, 07160802.

Further Online information:

Tylopilus rubrobrunneus in Smith & Thiers, 1971

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Cite this page as:

Kuo, M. (2007, February). Tylopilus rubrobrunneus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/tylopilus_rubrobrunneus.html