|Major Groups > Boletes > Boletus > Edulis Group > Xanthoconim separans|
Xanthoconium separans (Boletus separans)
by Michael Kuo
Here is an attractive and fairly easily identified bolete, found under hardwoods east of the Rocky Mountains. Crucial features include its yellow (not olive) mature pore surface, and the distinctive, liver-red flush on the stem. The young caps are also often colored liver-red, but they soon fade and become brownish to yellowish brown.
To be certain of your identification, place a drop of common household ammonia on the stem of Xanthoconium separans: the result is a color change to deep blue-green (click here for more information on chemical testing). In its paler forms, Xanthoconium separans might be confused with several species in the Boletus edulis group, but the other species in the group do not develop the liver colored hues on the stem, and do not flash green with ammonia.
This mushroom is called Boletus separans in many field guides.
Ecology: Mycorrhizal with hardwoods (especially oaks), sometimes with conifers; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains.
Cap: 5-20 cm; convex to broadly convex in age; dry; usually somewhat wrinkled; the margin often with a very small projecting sterile portion; color variable but typically lilac-brown or liver-red when young, becoming yellowish brown in age.
Pore Surface: White when young, becoming yellowish and finally brownish; not bruising; pores "stuffed" when young; at maturity with 1-2 circular pores per mm; tubes to 3 cm deep.
Stem: 6-15 cm long; 1-3 cm thick; more or less equal, or tapering somewhat to apex; solid; smooth or slightly wrinkled; not prominently reticulate in most collections, but faintly to prominently reticulate at times; pale at apex, but flushed with the color of the young cap below.
Flesh: Whitish throughout, unchanging on exposure or bruising.
Odor and Taste: Not distinctive.
Chemical Reactions: Cap surface and stem (where liver colored) deep blue-green with ammonia; dingy greenish with KOH.
Spore Print: Brownish to pale reddish brown or yellowish brown.
Microscopic Features: Spores 12-16 x 3.5-5 µ; smooth; subfusiform. Pileipellis a tightly packed trichoderm with clavate or subclavate terminal elements--an "epithelium" or hymeniform turf.
REFERENCES: (Peck, 1873) Halling & Both, 1998. (Saccardo, 1888; Coker & Beers, 1943; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Arora, 1986; Phillips, 1991/2005; Both, 1993; Halling & Both, 1998; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Kuo, 2007.) Herb. Kuo 07299701, 08270206, 08240504, 07060703.
Boletus separans is a synonym. "Boletus nobilis," in the sense of some authors (e.g. Snell & Dick, 1970), is a synonym. Boletus pseudoseparans is a probable synonym.
Further Online Information:
Cite this page as:
Kuo, M. (2004, December). Xanthoconium separans / Boletus separans. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xanthoconium_separans.html