|Major Groups > Boletes > Xerocomellus chrysenteron|
by Michael Kuo
This well known bolete features a brown to olive brown cap that quickly begins to develop a cracked, mosaic-like surface in which pinkish flesh is exposed in the cracks. Other distinguishing features include its small to medium size, its general stature (the stem is usually longer than the cap is wide), its usual-but-not-exclusive preference (in North America, anyway) for hardwoods, and microscopic features (see below). Xerocomellus chrysenteron is undoubtedly a collective species in North America, and none of our versions may actually match the original, European species first described from France.
In Europe several species have recently been segregated from Xerocomellus chrysenteron--including Xerocomellus cisalpinus and a newly re-defined Xerocomellus communis. In North America, one segregate species, Xerocomellus truncatus, was named in 1959; it is virtually identical to the naked eye, but associates primarily with conifers and features truncated spores. Others are likely to be discovered (and even Xerocomellus truncatus may require splitting up once DNA studies look closely, since it is found in diverse ecosystems across the continent, and mycorrhizal species often tend to be fairly host-specific).
Ecology: Mycorrhizal with hardwoods, especially oaks, and also sometimes reported with conifers; growing alone, scattered, or gregariously; summer and fall, or in winter in warm climates; widely distributed in North America. The illustrated and described collections are from Michigan, Illinois, Ohio, and California.
Cap: 2-7 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, or rarely reddish overall, in old age; marginal area often reddish in age.
Pore Surface: Yellow when young, becoming brownish or olive; bruising blue, sometimes slowly; with 1-3 angular pores per mm; tubes to 5 mm deep.
Stem: 3-7 cm long; 0.5-1.5 cm thick; more or less equal, or tapering to a pinched base; solid; yellow above, pinkish reddish below; purplish red at base; basal mycelium white to yellowish; not reticulate, but sometimes with broad longitudinal ridges.
Flesh: Whitish to pale yellow 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 on flesh.
Spore Print: Brown to dark olive brown.
Microscopic Features: Spores 10-14 x 3-4 µ; smooth; subfusiform; golden in KOH. Hymenial cystidia fusoid-ventricose to fusoid; to 45 x 15 µ; yellow in KOH. Pileipellis a tightly packed trichoderm; elements brown in KOH, encrusted, 2.5-5 µ thick; terminal cell often browner and more narrow.
REFERENCES: (Bulliard, 1791) Šutara, 2008. (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; McNeil, 2006; Miller & Miller, 2006; Trudell & Ammirati, 2009; Kuo & Methven, 2014.) Herb. Kuo 07189401, 09260903, 07271202, 01141501.
Boletus chrysenteron and Xerocomus chrysenteron are synonyms.
Further Online Information:
Cite this page as:
Kuo, M. (2014, December). Xerocomellus chrysenteron. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xerocomellus_chrysenteron.html