BOLETUS SUBTOMENTOSUS Fries, Syst Mycol., p. 389. 1821
Xerocomus subtomentosus (Fries) Quelet, Fl. Mycol. Fr. p. 418.1888.
Ceriomyces subtomentosus (Fries) Murrill, Mycologia 1:153.1909.
Ceriomyces oregonensis Murrill, Mycologia 4:97. 1912.
Illustrations: See Microfiche No. 21
Kawamura, S., Icones of Japanese Fungi, pl. 237.
Lange, J. E., and M. Lange, 600 Pilze in Farben, p. 188.
Leclair, A., and H. Essette, Les Bolets, pl. 24.
Romagnesi, H., Nouvel Atlas des Champignons, pl. 124.
Singer, R., Die Rohrlinge, Teil 1, pl. XII, figs. 13-15.
Smith, A. H., and H. D. Thiers, The Boletes of Michigan, pl. 104.
Snell, W. H., and E. A. Dick, The Boleti of Northeastern North America, pl. 26.

Pileus 6-15 cm broad at maturity, convex becoming broadly convex to plano-convex to plane or shallowly depressed at maturity; surface dry, dull, velutinous to subtomentose to matted tomentose during all stages of development, usually not conspicuously areolate but sometimes rimose at least on the margin; color when young yellow brown to olive brown ("Isabella color" to "tawny olive" to (,clay color") to occasionally yellow ("yellow ocher" to "antimony yellow"), usually becoming darker brown ("sayal brown" to "snuff brown" to "buckthorn brown" to "olive-ocher") with age, no reddish pigmentation along the margin or in cracks in the flesh; margin entire, incurved to decurved, sometimes staining dark brown when handled. Context 1-2.5 cm thick, firm, whitish to pale yellow, often concolorous with the cuticle near the surface, typically changing to blue when exposed. Taste mild to slightly acid; odor not distinctive.

Tubes 1-2 cm long, adnexed to arcuate-decurrent when young, becoming shallowly to deeply depressed with age; when young bright yellow to buff ("antimony yellow" to "warm buff"), changing to deeper yellow ("primuline yellow" to "amber yellow" to "honey yellow" to "olive-ocher") with age, changing to blue when bruised; pores large, 1-2 mm, angular to highly irregular in outline, often compound, concolorous with tubes or rarely reddish.

Stipe 5-11 cm long, 1-2.5 cm thick at the apex, equal or sometimes narrowing at the base, solid, often with whitish to yellow mycelium and yellow rhizoids arising from the base; surface dry, glabrous to granulose to appressed fibrillose or longitudinally ridged, sometimes obscurely reticulate at the apex; color yellow ("Naples yellow") at the apex, becoming rust colored ("tawny" to "ochraceous-tawny") in the midportion and pallid ("warm buff") at the base, occasionally with a yellow background color, but heavily overlain with darker colored granulations. Context whitish to pale yellow, typically changing to blue when exposed.

Spore print olive brown. Spores 11.5-16 X 3.5-5 µm, pale yellow ochraceous in KOH, smooth, thin-walled, subfusoid to subcylindric.

Basidia 27-32 X 7-9 Ám, clavate, hyaline in KOH, four-spored. Hymenial cystidia 40-66 X 8-12 Ám, scattered to numerous, hyaline, thin-walled, fusoid to fusoid-ventricose, often with elongated, tapering apices.

Tube trama obscurely divergent to subparallel, with numerous laticiferous hyphae interspersed, hyphae ▒5 Ám wide. Pileus trama interwoven, homogeneous except for interspersed laticiferous hyphae. Pileus cuticle pale ochraceous yellow in Melzer's reagent and KOH, a more or less tangled trichodermium with numerous free, septate hyphal tips, usually strongly incrusted, hyphae 5-7 Ám wide. Stipe cuticle differentiated as a layer of free to loosely interwoven hyphal tips with occasional tufts or clusters of caulocystidia 24-40 X 6-9 Ám, which are hyaline, fusoid to clavate, thin-walled. Clamp connections absent.

Chemical reactions KOH-context negative to pale yellow, cuticle darkening slightly; NH4OH-cuticle negative to darkening slightly; HCl-cuticle pink; HNO3-context negative to pale yellow, cuticle dark red to pink; sulfoformal in-cuticle pink; FeSO4-context negative or becoming pale gray.

Habit, habitat, and distribution Solitary to gregarious in soil in the coastal forests; often appearing along road cuts or similarly disturbed areas. It has only been found in abundance along the northern coast, but occasional collections have been made elsewhere within the state. Fruiting only during the fall-winter rainy season.

Material studied Del Norte County: Smith 55944; Sundberg 959; Thiers 14305, 17766. Humboldt County: Thiers 13974, 14190, 24148, 24305. Marin County: Madden 747; Thiers 7534, 10872, 11145. Mendocino County: Thiers 8180, 8396, 8405, 8876, 8877, 9061, 9262, 9292, 9309, 9337, 9348, 9438, 9471, 9767, 10573, 10647, 10676, 11019, 14595, 14615, 14616, 14619, 18403, 18496, 21772. San Mateo County: Sundberg 392; Thiers 8670, 10926, 11937, 18189, 21905. Santa Barbara County: Thiers 11798. Santa Cruz County: Thiers 8694, 10756, 10771, 10959, 10964, 18542. Siskiyou County: Thiers 23020.

Observations The dark-olive to yellow-olive color of the pileus, which is tomentose to velutinous, the bright-yellow tubes, which typically change to blue when bruised, the large, typically compound pores, and the more or less yellow stipe make this species distinct. In older, areolate pilei there is no appreciable development of red pigments in the cracks as in B. chrysenteron. The failure of ammonium hydroxide solution to give a blue discoloration on the cuticle of the pileus likewise distinguishes it from B. spadiceus. When compared with midwestern or eastern collections of B. subtomentosus, California material seems to be more heavily pigmented, particularly with olive tones, and to fade only slightly when dried.

An examination of the type of Ceriomyces oregonensis, described by Murrill from near Newport, Oregon, has revealed no significant differences from B. subtomentosus, and it is, consequently, reduced to synonymy with it.

Edible and considered good by some.

Online edition addendum

Other Descriptions and Photos: The Fungi of California

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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