BOLETUS FLAVIPORUS Earle, Bull. N.Y. Botan. Garden 3:297. 1905
Ceriomyces flaviporus (Earle) Murrill, Mycologia 1:147. 1909.
Pulveroboletus flaviporus (Earle) Singer, Am. Midland Nat. 37:17. 1947.
Illustrations: See Microfiche No. 11

Pileus 7-15 cm broad at maturity, convex when young, with age plano-convex to plane to somewhat depressed on the disc and flared to highly irregular on the margin; surface viscid to subviscid during all stages of development, tomentose or apparently appressed-fibrillose, sometimes appearing glabrous, often reticulate to irregularly rugose, rarely fibrillose-scaly on the margin with age; color when young reddish brown ("hazel" to "vinaceous-tawny" to "orange-cinnamon"), with age darkening to dark reddish brown ("mahogany red" to "bay" to "chestnut") to sometimes dark brown ("seal brown" to "light seal brown") on the disc and fading to brown ("warm sepia" to "Verona brown" to "Mars brown") on the margin; margin entire, incurved, glabrous. Context 1-2 cm thick, white to pale pink ("pale pinkish buff"), unchanging when exposed or slowly becoming pinkish vinaceous ("testaceous" to "avellaneous"). Taste acid, somewhat unpleasant; odor mild.

Tubes 1-2 cm long, broadly and shallowly depressed, yellow ("yellowish citrine" to "pale green-yellow" to "light chalcedony yellow"), unchanging when exposed; pores 1 mm or more broad, angular, intense yellow ("strontian yellow" to "light greenish yellow" to "greenish yellow"), unchanging or darkening slightly when bruised.

Stipe 6-15 cm long, 1-3(4) cm thick at the apex, equal to clavate to tapering toward the base, solid, with conspicuous white mycelium at the base; surface viscid in wet weather, dry to subviscid otherwise, tubes forming a distinct, raised, yellow network at the apex, glabrous to punctate-roughened to occasionally fibrillose or fibrillose-scaly, sometimes ridged or obscurely reticulate; color yellow ("massicot yellow") at the apex, becoming white to pallid to nearly concolorous with the pileus, base typically white. Context white, unchanging.

Spore print dark olive brown. Spores 11-15 X 4-6 Ám, pale ochraceous in KOH, cylindric to obscurely fusoid, smooth, thin-walled.

Basidia 23-29 X 8-12 Ám, hyaline, clavate, four-spored. Hymenial cystidia 48-70 X 9-15 Ám, scattered to numerous, hyaline, thin-walled, clavate to obscurely fusoid-ventricose, often appearing incrusted at the apex.

Tube trama hyaline, slightly divergent to subparallel. Pileus trama interwoven, homogeneous. Pileus cuticle differentiated as a pellicle of interwoven gelatinous hyphae, 3-4 Ám wide. Stipe cuticle formed by a layer of interwoven, gelatinous hyphae with scattered areas in which the terminal cells are differentiated as enlarged clavate cells, 40-50 X 15-20 Ám. Clamp connections absent.

Chemical reactions NH4OH-context pale lavender; FeSO4-context pale gray.

Habit, habitat, and distribution Solitary to scattered to occasionally cespitose in soil in mixed or hardwood forests. This bolete seems to be associated primarily with madrone, but occasional collections have been made under oaks. It has been found in the coastal area from Santa Barbara County northward to Mendocino County. The type was described from the Santa Cruz Peninsula, where it is abundant. Isolated collections have also been made in Napa, Sacramento, and Shasta counties. Surprisingly, no published reports have been found of its occurrence in other Pacific states. It fruits most commonly during the fall season, but single basidiocarps have been collected as late as April.

Material studied Marin County: Thiers 7523, 9827, 10871. Mendocino County: Thiers 21504. Napa County: Dusatko 7; Peters 325. Sacramento County: Thiers 32137. San Mateo County: Peters 156; Thiers 8546, 8547, 8663, 11818, 11918, 11965, 12173, 14652, 14837, 18063. Santa Barbara County: Thiers 18573. Santa Cruz County: Sundberg 201; Thiers 10772, 18549. Shasta County: Thiers 21606. Sonoma County: Thiers 9409, 10772.

Observations Boletus flaviporus is one of our most distinctive species and is easily recognized by the very intense yellow color of the pores, the viscid, cinnamon-colored pileus, and the pallid stipe, which is often punctate-roughened at least when young. Apparently, its nearest relative is B. auriporus, which is not known west of the Rocky Mountains. That species is much smaller, has a differently colored pileus, and a nonviscid stipe. In California, B. flaviporus is not likely to be confused with any other species.

The placement of this species in the genus Pulveroboletus seems to be indefensible. No evidence of a veil or pulverulence during any stage of development has been observed on any of the numerous collections examined. The fragments or appendiculations noted by Singer on old dried material could conceivably be artifacts resulting from the drying process.

Edibility unknown. Since B. auriporus is considered edible, this species is possibly safe, but, perhaps, not of a pleasing taste or texture.

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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