Pileus 6-15 cm broad at maturity, convex, becoming broadly convex to plano-convex to highly irregular in outline; surface dry, velutinous to finely tomentose and sometimes with a band of pallid, appressed fibrillose scales toward the margin when young, usually becoming glabrous to subglabrous with age, generally areolate to rimose-areolate when older; color olive brown to brown ("cinnamon" to "buffy brown" to "wood brown") on the disc, fading to buff ("olive-buff" to "pale olive-buff" to "warm buff") toward the margin; margin entire, incurved. Context 1-3 cm thick, yellow ("primrose yellow" to "cream color") changing to blue when exposed; taste and odor mild.
Tubes 0.5-1 cm in length, when young bright yellow ("primuline yellow") changing to dark yellow ("colonial buff" to "old gold") when older, bluing when bruised; pores up to 1 mm broad, angular, concolorous with tubes, bluing when bruised.
Stipe 4-10 cm long, 1-3.5 cm thick at apex, equal to subclavate to sometimes tapering slightly at the base, solid; surface dry, glabrous to obscurely furfuraceous to punctate, not reticulate; color yellow ("primrose yellow") at the apex, changing to tan ("warm buff" to "buffy brown") toward the base, occasionally with a reddish band at the apex. Context yellow to concolorous with the surface, bluing when bruised.
Spore print dark olive brown. Spores 13-17.5 X 5-7.8 Ám, subfusoid, to subcylindric in face view, ventricose in side view, ochraceous in KOH and Melzer's, smooth, thin-walled.
Basidia 28-35 X 6-9 Ám, hyaline in KOH, clavate, four-spored. Hymenial cystidia apparently not differentiated.
Tube trama strongly divergent from a narrow central strand, hyaline in KOH, dark ochraceous in Melzer's, hyphae 4-6 Ám wide, often with scattered laticiferous hyphae. Pileus trama homogeneous, interwoven. Pileus cuticle differentiated as a trichodermium of loosely interwoven hyphae with occasional free hyphal tips, hyphae 5-7 Ám wide, with abundant hyaline, spiral incrustations that are ochraceous in KOH, bright ochraceous in Melzer's. Stipe cuticle differentiated as a layer of fertile basidia with scattered caulocystidia 27-35 X 8-12 Ám, which are hyaline, thin-walled, fusoid to fusoid-ventricose in outline. Clamp connections absent.
Chemical reactions unknown.
Habit, habitat, and distribution Scattered to solitary in soil under conifers. This species is very uncommon in California and has been found only in the Yuba Pass and Luther Pass areas.
Material studied El Dorado County: Thiers 32756. Sierra County: Thiers 21142, 21181, 23637.
Observations This is one of the large, massive boletes that occurs, as far as is known, only in the alpine areas, where it appears to be associated with red fir. It is distinguished by the dull, brown pileus, pallid flesh that stains blue, and a nonreticulate stipe. It is most likely to be confused with B. calopus, but can be easily distinguished from it by the smooth rather than reticulate stipe.
The California species differs from the European species in the apparent mycorrhizal associate. Almost invariably it is reported as associated with oaks in Europe, whereas in California it is only found under conifers. Since no other significant difference has been observed, the present disposition of this species seems to be the most satisfactory.
The European species is edible according to Bresadola; however, the edibility has not been determined for the California specimens.
The Boletes of California
Copyright © 1975 by Dr. Harry D. Thiers
Additional content for the online edition © 1998 by Michael Wood, Fred Stevens, & Michael Boom
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