Pileus 4-10 cm broad at maturity, convex to plano-convex during all stages of development; surface dry, dull, velutinous to subtomentose to tomentose during all stages of development; color when young brown to reddish brown ("Kaiser brown" to "russet" to as pale as "dark olive-buff"), with age usually becoming dark brown ("Kaiser brown" to "Dresden brown" to "cinnamon-brown") or fading to pale yellow brown ("Isabella color"), often retaining a reddish tint and appearing dark reddish brown when wet; margin incurved to decurved, entire. Context 1-1.5 cm thick, pale vinaceous near cuticle and yellow above the tubes, otherwise white, unchanging when exposed, or slowly changing to blue near the tubes. Taste and odor mild.
Tubes 1-1.5 cm in length, depressed to subdecurrent, yellow ("wax yellow" to "strontian yellow" to "mustard yellow"), changing to blue when bruised or exposed; pores 1-2 mm broad, often compound, angular, concolorous.
Stipe 5-15 cm long, 1-2 cm thick at the apex, equal to tapering toward the base, solid; surface dry, often coarsely reticulate in apical portion, smooth to longitudinally ridged toward the base; color pale yellow to buff ("ochraceous-buff" to "baryta yellow") to occasionally almost white, sometimes with brownish stains. Context white to pale yellow, unchanging or slowly changing to blue when exposed.
Spore print dark olive brown. Spores 9-11 X 4-5.5 Ám, pale ochraceous in KOH and Melzer's, subfusoid to subellipsoid in face view, inequilateral and ventricose in profile, walls smooth, thin.
Basidia 20-30 X 4-6 Ám, four-spored, hyaline, clavate. Hymenial cystidia 40-55 X 4-7 Ám, numerous, conspicuous, projecting from the hymenium, clavate to fusoid to fusoid-ventricose, hyaline, thin-walled.
Tube trama obscurely divergent, hyaline, inamyloid, hyphae 6-7 Ám. Pileus trama homogeneous, interwoven, inamyloid. Pileus cuticle differentiated as a trichodermium of suberect to tangled to repent hyphal tips, irregularly incrusted, ochraceous in KOH, rust red in Melzer's. Clamp connections absent.
Chemical reactions NH4OH-cuticle blue, becoming fuscous; KOH-context orange yellow, cuticle dark brown.
Habit, habitat, and distribution Gregarious to solitary in soil in dense mixed coastal forests of northern California. It has also been collected in San Diego County.
Material studied Mendocino County: Thiers 24193, 26930. Napa County: Thiers 27005. San Diego County: Thiers 25234. San Mateo County: Thiers 26919, 26935, 26957, 26987, 26993, 27016. Santa Cruz County: Thiers 26968, 27052.
Observations This species is often confused with B. subtomentosus, but is most easily distinguished from it by the blue to blue-green discoloration of the surface of the pileus when ammonium hydroxide solution is applied. Also B. spadiceus often has more reddish pigment in the pileus and typically appears reddish brown when wet. Unfortunately, there is considerable variance in the concept of this species. Watling does not generally subscribe to the same species concept as that of most Americans and, as a matter of fact, specifically indicates that B. spadiceus does not show a blue discoloration with NH4OH. He places fungi with this character in B. lanatus. However, until further data are available the present concept, which is accepted by both Smith and Singer, will be followed.
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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