Pileus 3-14 cm broad, convex when young, becoming broadly convex to plano-convex to plane with a decurved margin with age; surface dry, dull, velutinous to tomentose, typically becoming rimose with age and then sometimes appearing fibrillose or fibrillose-scaly; color dark olive brown to grayish brown ("olive-brown" to "citrine-drab" to "olive-buff"), unchanging or changing only slightly with age, cracks typically pallid ("warm buff" to "light buff"), no reddish pigmentation apparent; margin entire, incurved, becoming broadly decurved to plane. Context 0.5-1 cm thick, yellow to pallid ("pale olive-buff" to "warm buff"), erratically changing to blue when exposed, or sometimes unchanging. Taste and odor mild.
Tubes 1-2 cm long, depressed around the stipe, yellow ("Isabella color" to "olive-ocher" to "old gold"), staining blue when bruised; pores approximately I mm broad, angular, typically concolorous with the tubes or often with reddish discolorations, staining blue when bruised.
Stipe 5-10 cm long, 1-2 cm thick at apex, equal to tapering slightly toward the base, occasionally slightly flared at the apex, with yellow mycelium at the base, solid; surface dry, usually with small dots or flecks, but never truly fibrillose or tomentose, background color pale tan or pallid ("warm buff" to "pale olive-buff"), but this color often masked with reddish punctations or scales. Context yellow to occasionally red in midportion, unchanging when exposed.
Spore print dark reddish brown. Spores 13-17.6 X 4-6.5 Ám, fusoid to subcylindric, often with considerable pleomorphism, amyloid, varying from only slightly so to (in one collection) strongly so, apex typically thickened and noticeably truncate, with a thin-walled depression in the center, walls smooth.
Basidia 30-35 X 8-12 Ám, four-spored, clavate, hyaline. Hymenial cystidia 43-55 X 9-14 Ám, scattered, hyaline, thin-walled, clavate with a tapering, subacute apex to near fusoid.
Tube trama obscurely divergent, hyaline in KOH, laticiferous hyphae usually present. Pileus trama interwoven, hyaline in KOH, laticiferous hyphae present. Pileus cuticle differentiated as a trichodermium of tangled hyphal tips, ochraceous in KOH, with somewhat irregularly incrusted, terminal cells 10-15 Ám wide. Clamp connections not seen.
Chemical reactions unknown.
Habit, habitat, and distribution Solitary to scattered in humus in mixed northern coastal forests.
Material studied Mendocino County: Thiers 18511. San Mateo County: Thiers 23136, 27019. Santa Cruz County: Thiers 18547.
Observations This bolete is rather similar in appearance to members of the Boletus truncatus-B. chrysenteron complex, and in some cases can only be accurately distinguished from them by obtaining a good spore deposit. As indicated, the spores of T. amylosporus are dark reddish brown in mass, whereas in the others they are olive brown. The amyloid reaction of the spores of T amylosporus often appears somewhat erratic and may vary from strongly positive to weakly so, or almost nonamyloid. In the B. truncatus-B. chrysenteron complex, however, the spores are consistently nonamyloid.
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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