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Boletus bicolor

[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

Boletus bicolor, the "two-colored bolete," is a beautiful bolete with starkly contrasting red and yellow colors, found primarily east of the Rocky Mountains. It is a medium-sized to large mushroom, which helps to distinguish it from the many similar species with smaller stature (Boletus rubellus, Boletus campestris, and others). The bright yellow pore surface of Boletus bicolor discolors deep indigo when bruised, but its flesh discolors less dramatically blue when exposed. The tube layer is very shallow in comparison to most boletes. The stem is yellow near the apex, and colored like the cap below. It is not reticulate.

Description:

Ecology: Mycorrhizal with oaks and other hardwoods; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains.

Cap: 5-15 cm, convex to broadly convex in age, sometimes irregular; dry; smooth, like soft leather; becoming cracked; deep brick red to pinkish red, sometimes yellowish near the margin.

Pore Surface: Bright yellow; sometimes with reddish stains; bruising blue quickly or slowly; tubes shallow (often measuring under 1 cm long even in large specimens).

Stem: 5-10 cm long; 1-3 cm thick; more or less equal; solid; smooth; yellow at apex; colored like the cap below.

Flesh: Yellow throughout; bruising slowly pale blue when exposed.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia negative on cap, negative to brown on flesh; KOH negative on cap, pale orange to brownish on flesh; iron salts blackish on cap, gray to olive on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 8-12 x 3.5-5 µ; smooth; subfusiform.

REFERENCES: Peck, 1872. (Saccardo, 1888; Coker & Beers, 1943; Snell & Dick, 1970; Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Both, 1993; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Binion et al., 2008.) Herb. Kuo 07089505, 08310102.

Several varieties are recorded in the literature: Boletus bicolor var. borealis, a northeastern variety with a red to orangish red pore surface and larger (11-15 x 4-5 µ) spores; and Boletus bicolor var. subreticulatus, which is reticulate over the upper third of the stem. See also the similar Boletus bicoloroides, and Boletus pallidoroseus.

Further Online Information:

Boletus bicolor and varieties in Smith & Thiers, 1971
Boletus bicolor at Roger's Mushrooms

 

Boletus bicolor

Boletus bicolor

Boletus bicolor



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Kuo, M. (2003, August). Boletus bicolor. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_bicolor.html