Pileus 4-7.5 cm latus, siccus, subtomentosus, obscure rufobrunneus. Contextus albus tactu immutabilis. Tubuli 0.5-1 cm longi, flavi tactu caerulei; pori 1 mm lati, concolores tactu subcarnei. Stipes 4-6 cm longus, 1-1.5 cm crassus, siccus, glaber, subflavus. Sporae 11.5-15 X 5-5.5 µm, ellipsoideae vel subfusoideae. Cystidia 25-33 X 5-10 µm, fusoidea vel submucronata vel subclavata. Cuticula e hyphis rectis, clavatis, composita. Holotypus (no. 17766) a H. D. Thiers lectus prope Jedediah Smith Redwoods State Park, Del Norte County, November 12, 1966; in Herbarium San Francisco State University conservatus.

Pileus 4-7.5 cm broad at maturity, convex when young, becoming plano-convex to broadly convex at maturity; surface dry, dull, subtomentose to velutinous during all stages of development; color dark reddish brown ("auburn" to "Hessian brown" to "liver brown" to occasionally "chestnut-brown") during all stages of development; margin incurved, entire. Context 0.5-1 cm thick, white, unchanging when exposed. Taste and odor mild.

Tubes 0.5-1 cm in length, adnate to depressed, intensely yellow ("chamois" to "reed yellow"), unchanging with age, staining blue when exposed or bruised; pores up to 1 mm broad, appearing compound, concolorous with tubes, somewhat boletinoid, staining pale lavender to flesh color ("avellaneous" to "testaceous") when bruised.

Stipe 4-6 cm long, 1-1.5 cm thick at the apex, equal or tapering toward the base, solid, yellow rhizoids at the base; surface dry to moist, glabrous during all stages of development, pale yellow ("ivory yellow"), staining yellow brown or fulvous when bruised. Context white, unchanging when exposed.

Spore print color unknown. Spores 11.5-15 X 5-5.5 Ám, pale ochraceous in KOH and Melzer's, ellipsoid to subfusoid in face view, inequilateral and ventricose in profile, not truncate, walls thin, smooth.

Basidia 21-27 X 5-8 Ám, four-spored, clavate, giving a fleeting amyloid reaction when first mounted in Melzer's, soon becoming hyaline. Hymenial cystidia 25-33 X 5-10 Ám, numerous, hyaline, pale ochraceous in Melzer's, fusoid to submucronate to subclavate, thin-walled.

Tube trama slightly divergent, giving a strong fleeting amyloid reaction when first mounted in Melzer's, quickly fading to hyaline, hyphae 4-5 Ám wide. Pileus trama interwoven, homogeneous, nonamyloid, hyaline in KOH. Pileus cuticle differentiated as a trichodermium of erect, closely packed, clavate hyphal tips, heavily incrusted, not spirally arranged, incrustations staining bright red ("tawny") in Melzer's. Clamp connections absent.

Chemical reactions NH4OH-cuticle greenish blue, changing to fuscous.

Habit, habitat, and distribution Gregarious in soil in dense mixed conifer-hardwood forest. It is known only from the coastal forest near Crescent City.

Material studied Del Norte County: Thiers 17766 type.

Observations This variety is distinguished by the reddish-brown color of the pileus and the amyloid reaction in the tube trama and hymenium. Boletus spadiceus var. gracilis, recently described from Michigan, has a similar amyloid reaction, but does not have a similarly colored pileus.

Edibility undetermined.

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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