|Major Groups > Boletes > Boletus > Xanthoconium affine|
Xanthoconium affine (Boletus affinis)
by Michael Kuo
Also known as "Boletus affinis," this bolete is found in hardwood forests east of the Rocky Mountains, and in Mexico. It has a yellowish brown spore print--which, along with the structure of the cells on its cap surface, places it in the genus Xanthoconium in the current taxonomic arrangement of boletes (however, the concept of Xanthoconium has not been supported by DNA studies).
Defining features for Xanthoconium affine include the brown cap and yellowish mature pore surface, along with the absence of any dramatic bruising or staining. A drop of ammonia applied to the cap surface produces a boring, orangish or tan reaction--helping to separate it from the very similar, reddish-capped Xanthoconium purpureum, which demonstrates a green flash with ammonia.
Ecology: Mycorrhizal with hardwoods and perhaps rarely with conifers; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains, south to Mexico.
Cap: 5-10 cm, convex to broadly convex in age; dry; smooth or very minutely velvety; brown to dark brown or yellow-brown; sometimes spotted with whitish to yellowish spots ("var. maculosus").
Pore Surface: Whitish, becoming yellowish brown; not bruising, or bruising dull yellowish brown; pores circular; tubes to 1.5 cm deep.
Stem: 5-12 cm long; 1-2.5 cm thick; more or less equal; solid; smooth; pale at apex, streaked with a paler shade of the cap color below.
Flesh: Whitish throughout, occasionally staining slightly yellowish on exposure.
Odor and Taste: Not distinctive with most specimens; odor not distinctive or with a rather foul and distinctive "old bolete" odor when past maturity.
Chemical Reactions: Cap surface rusty tan with ammonia; flesh olive gray with iron salts.
Spore Print: Bright yellow-brown.
Microscopic Features: Spores 11-16 x 3-4 µ; smooth; swollen in the middle or nearly cylindric. Pileipellis a tightly packed trichoderm with clavate or subclavate terminal elements--an "epithelium" or hymeniform turf.
Boletus affinus is a synonym.
REFERENCES: (Peck, 1872) Singer, 1944. (Saccardo, 1888; Coker & Beers, 1943; Singer, 1947; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Kuo, 2007.) Herb. Kuo 07189402.
Several varieties of Xanthoconium affine have been described. Xanthoconium affine var. maculosus is more or less identical but has a cap that is spotted with whitish or pale yellow spots--while Xanthoconium affine var. reticulatum has a conspicuously reticulate stem. However, I have collected similar reticulate and spotted "varieties" of Xanthoconium purpureum--supporting the idea that one variable species might account for Xanthoconium purpureum and all the varieties of Xanthoconium affine.
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Cite this page as:
Kuo, M. (2007, December). Xanthoconium affine / Boletus affinis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xanthoconium_affine.html