Xerocomellus diffractus
Fungal Systematics and Evolution 6: 278. 2020.
Common Name: none
Misapplied names: Boletus chyrsenteron Bull.; Xerocomus chrysenteron (Bull.) Quélet; Xerocomellus chrysenteron (Bull.) Šutara
Cap 4-9 cm broad, convex, becoming nearly plane in age; surface dry, tomentose, dark brown to olive brown, soon areolate, the exposed context pallid at the disc, pinkish near the margin; flesh white, thick, sometimes blueing when bruised; odor mild, taste acidic.
Pores relatively large, 1-2 mm, yellow, olive-brown in age, typically bruising blue.
Stipe 5-10 cm tall, 1.0-1.5 cm thick, dry, smooth to longitudinally ridged, yellowish, with reddish tints usually predominating at the base.
Spores 11.5-14.0 x 4-6 µm, smooth, elliptical to fusiform; spore print olive-brown.
Solitary or in small groups in hardwood/conifer woods from early fall to mid-winter.
Edible, of fair quality.
This drab member of the Bolete clan is recognized by a dark brown-brown to olive-brown areolate cap, and slow, not always consistent blueing of the tubes and cut flesh. Xerocomellus truncatus is a closely related species that stains quickly and intensly blue and with cracks in the cap context tending not to turn pink as in X. diffractus. To confirm an identification requires an examination of spores. In Boletus truncatus, as the name suggests, the spores are either blunt or truncate at one end, while in B. diffractus they are rounded. Another related species is Xerocomellus atropurpureus, but it has a darker, less cracked cap at maturity, and a more uniformly red stipe.
Until recent work by Frank et al., this species was known as Xerocomellus chrysenteron, a morphologically similar, but genetically distinct species that appears to be restriced to Europe.
Arora, D. (1986). Mushrooms Demystified. Ten Speed Press: Berkeley, CA. 959 p.
Bessette, A.E., Roody, W.C. & Bessette, A.R. (2000). North American Boletes: A Color Guide to the Fleshy Pored Mushrooms. Syracuse University Press: Syracuse, NY. 400 p.
Breitenbach, J. & Kränzlin, F. (1991). Fungi of Switzerland. Volume 3: Boletes and Agarics (1st Part). Strobilomycetaceae, Boletaceae, Paxillaceae, Gomphidiaceae, Hygrophoraceae, Tricholomataceae, Polyporaceae (lamellate). Verlag Mykologia: Luzern, Switzerland. 361 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Frank, J., Siegel, N., Schwarz, C., Araki, B. & Vellinga, E. (2020). Xerocomellus (Boletaceae) in western North America. Fungal Systematics and Evolution 6: 265-288. (PDF...Protologue)
Ladurner, H. & Simonini, G. (2003). Xerocomus s.l. Edizioni Candusso: Alassio. 527 p.
Siegel, N. & Schwarz, C. (2016). Mushrooms of the Redwood Coast. Ten Speed Press: Berkeley, CA. 601 p.
Smith, A.H. & Thiers, H.D. (1971). The Boletes of Michigan. University of Michigan Press: Ann Arbor, MI. 426 p.
Šutara, J. (2008). Xerocomus s. l. in the light of the present state of knowledge. Czech Mycol. 60(1): 29-62.
Thiers, H. D. (1975). California Mushrooms—A Field Guide to the Boletes. Hafner Press: New York, NY. 261 p. (WWW)
