LECCINUM BRUNNEUM Thiers, Mycologia 63:269. 1971

Pileus 6-10 cm broad, convex when young, becoming broadly convex to pulvinate to plano-convex to irregular in outline at maturity; surface dry, but may be viscid or subviscid in wet weather, dull, glabrous to finely subtomentose or obscurely appressed fibrillose, occasionally becoming somewhat fibrillose with age; color dark brown ("bister" to "warm sepia" to "Prout's brown"), sometimes somewhat paler brown ("cinnamon-brown" to "Verona brown" to "snuff brown") with age, drying dark dull brown; margin incurved, with conspicuous sterile cuticular flaps. Context 1-2.5 cm thick, white when first exposed, changing to fuscous with no reddish intermediate phase, fuscous color sometimes fading after prolonged exposure. Taste and odor mild.

Tubes 1-2 cm in length, depressed, white when young, becoming pale olive ("pale olive-buff") when mature, staining brown ("clay color" to "buckthorn brown" to "Mikado brown") when bruised, color fading in some after bruising; pores up to 1 mm broad, angular, concolorous.

Stipe 8-15 cm long, 1.5-3(4) cm thick at the apex, clavate, solid; surface dry, covered with small squamules, ground color white, squamules white at first, becoming darker with maturity. Context white when first exposed, then becoming fuscous directly as in the pileus, sometimes becoming blue in the base.

Spore print brown. Spores (14)15.5-19.5 X 4-6 Ám, ochraceous in KOH, some showing a dextrinoid reaction in Melzer's, fusoid to subcylindric to subellipsoid, inequilateral, walls smooth, moderately thick.

Basidia 30-35 X 7-11 Ám, hyaline in KOH, clavate to pyriform, four-spored. Hymenial cystidia 35-50 X 8-12 Ám, scattered to abundant, often inconspicuous; some staining pale brown in KOH and dark reddish brown in Melzer's, fusoid to fusoid-ventricose to clavate.

Tube trama hyaline, divergent from a distinct central strand, hyphae 3-7 Ám wide. Pileus trama interwoven, homogeneous, hyaline in KOH, hyphae 5-9 Ám wide. Pileus cuticle differentiated as a trichodermium of tangled hyphal tips; pale ochraceous in KOH, tawny to russet in Melzer's; hyphae 11-15 Ám wide, walls sometimes asperulate, pigment globules not forming when mounted in Melzer's, terminal cells relatively long and narrow, tapered somewhat at the tip. Caulocystidia 24-37 X 7-12 Ám clavate to fusoid to clavate with elongated, tapering apices, typically dark brown, but sometimes hyaline in KOH. Clamp connections absent.

Chemical reactions No distinctive reactions observed.

Habit, habitat, and distribution Gregarious to scattered in soil under aspens. Known only from the higher elevations in the Sierra Nevada, perhaps due to a similar distributional restriction of its only known mycorrhizal host.

Material studied Alpine County: Thiers 20818. El Dorado County: Thiers 20745, 20747, 20749, 20751, 20753, 20756, 20759, 20767. Mono County: Thiers 20963.

Observations The dull-dark-brown color of the pileus readily distinguishes this species. It is most likely to be confused with L. fibrillosum, but in L. brunneum the color changes of the exposed context are different and the pileus is not strongly fibrillose. The difference in the color of the cap and the lack of incrustations on the cuticular hyphae of L. brunneum distinguish it from L. obscurum. Leccinum subspadiceum, another brown species, is distinct because of the smaller spores, cinnamon-buff pores, and the yellow color in the dried stipe.

Edibility unknown.

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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