|Major Groups > Boletes > Boletus > Boletus chrysenteron|
by Michael Kuo
This common bolete is fairly widely distributed in North America, and can be recognized by its brown to olive brown, cracked cap; pinkish to reddish flesh is exposed in the cracks, separating it from most other boletes with oft-cracked caps. The two closest look-alikes are Boletellus chrysenteroides, which has a darker, brown cap and often grows from decaying wood--and Boletellus pseudochrysenteroides, which has a rosy red cap. Both of these look-alike species have ribbed spores, making them easily separable from Boletus chrysenteron with microscopic analysis.
I am treating two virtually indistinguishable (putative) species together here; Boletus chrysenteron is described below, followed by comments distinguishing Boletus truncatus.
Ecology: Mycorrhizal with hardwoods, especially oaks; growing scattered or gregariously; summer and fall, according to most authors; widely distributed in North America. According to Smith & Thiers (1971), growing "on earth exposed for 3-5 years, such as around uprooted trees, along roadsides, on mossy banks, etc., in hardwood and mixed forests, common during some seasons, rare during others" (260).
Cap: 3-8 cm; convex, becoming broadly convex or almost flat; dry; finely velvety when young; becoming cracked in age, usually conspicuously, with reddish to pinkish flesh showing in the cracks, especially towards the margin; brown to olive brown, rarely reddish overall; marginal area often reddish in age.
Pore Surface: Yellow when young, becoming brownish or olive, sometimes with reddish areas in age; bruising blue, sometimes slowly; with 1-2 angular pores per mm; tubes to 1 cm deep.
Stem: 4-7 cm long; .5-1 cm thick; more or less equal, or tapering to base; solid; yellow above, reddish below; purplish red at base; basal mycelium white to yellowish; not reticulate, but sometimes with a few ridges; bruising blue-green.
Flesh: White when young, yellow in age; staining slowly bluish on exposure.
Odor and Taste: Not distinctive.
Chemical Reactions: Ammonia negative to brownish on cap; negative to brownish on flesh. KOH negative to brown on cap; negative to brownish or orangish on flesh. Iron salts olive on cap; negative to yellow or olive on flesh.
Spore Print: Olive brown.
Microscopic Features: Spores 9-13 x 3.5-4.5 µ; smooth; subfusiform.
REFERENCES: Bulliard, 1791. (Saccardo, 1888; Coker & Beers, 1943; Snell & Dick, 1970; Smith & Thiers, 1971; Thiers, 1975; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; States, 1990; Phillips, 1991/2005; Lincoff, 1992; Both, 1993; Evenson, 1997; Barron, 1999; Bessette, Roody & Bessette, 2000; Wood & Stevens, 2003; McNeil, 2006; Miller & Miller, 2006; Trudell & Ammirati, 2009.) Herb. Kuo 07189401, 09260903.
Xerocomus chrysenteron is a synonym.
Boletus truncatus, also widely distributed, is virtually indistinguishable without a microscope; its spores are larger (10-15 x 5-7 µ) and frequently truncated, with a small apical pore. According to Wood & Stevens (2003), it is less likely to develop pinkish tones in the cracks, and bruises more quickly and intensely. Lincoff (1992) distinguishes Boletus truncatus microscopically and by its "abruptly tapering stalk base" (567).
Further Online Information:
Cite this page as:
Kuo, M. (2007, January). Boletus chrysenteron. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_chrysenteron.html