LECCINUM INSIGNE var. INSIGNE Smith, Thiers, and Watling, Mich. Botan. 5:160. 1966

Illustrations: See Microfiche No. 31
Smith, A. H., and H. D. Thiers, The Boletes of Michigan, pl. 77

Pileus 6-17 cm broad, convex to globose when young, becoming broadly convex to plano-convex to highly irregular with broad, shallow depressions or pits at maturity; surface dry to moist, occasionally subviscid in wet weather, glabrous to finely velutinous to subtomentose when young, unchanging or sometimes becoming obscurely appressed-fibrillose or fibrillose-scaly with age, frequently finely areolate to rimose-areolate when old; color somewhat variable, but typically some shade of reddish brown ("cinnamon" to "tawny" to "cinnamon-rufous" to "hazel" to "ferruginous" to as dark as "Kaiser brown" to as pale as "pinkish cinnamon"), often somewhat variegated with age; margin incurved, with noticeable sterile cuticular flaps. Context 1.5-3 cm thick, white when first exposed, changing to fuscous with no reddish intermediate stage, color changes sometimes very slow in developing. Taste and odor mild.

Tubes 1-2 cm long, narrowly depressed at first, becoming broadly and deeply depressed with age, somewhat ventricose in arrangement, white when young, olive buff ("pale olive-buff") to yellowish ("cartridge buff" to "chamois") when mature, staining brown when bruised; pores up to 1 mm broad, angular, concolorous.

Stipe 8-13 cm long, 1-2 cm thick at the apex, equal to clavate, solid; surface dry, squamulose, ground color white to whitish, squamules close and pallid when young, typically becoming dark brown to black and often more widely spaced at maturity, often very fine, and sometimes more or less collapsing with age. Context white, changing to fuscous as in pileus, blue discoloration sometimes developing in the base.

Spore print brown. Spores (11) 13-16(18) X 4-6 Ám, subfusoid to subcylindric, inequilateral, pale ochraceous in KOH, ochraceous in Melzer's, walls smooth, moderately thickened.

Basidia 29-34 X 8-12 Ám, hyaline in KOH, clavate to pyriform, four-spored. Hymenial cystidia 27-43 X 7-13 Ám, clavate to clavate with elongated, tapering apices, scattered to numerous, hyaline to dark brown in KOH.

Tube trama divergent from a distinct central strand, hyphae 3-5 Ám wide. Pileus trama homogeneous, interwoven, hyphae 8-12 Ám wide. Pileus cuticle differentiated as a trichodermium of tangled hyphal tips, hyphae 4-7 Ám wide, walls sometimes roughened, pigment globules not developing when mounted in Melzer's, terminal cells with obtuse apices, or with tapered apices. Caulocystidia 29-39 X 10-14 Ám, clavate to fusoid, dark brown in KOH, thin-walled. 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 and Cascades.

Material studied El Dorado County: Thiers 20746, 20748, 23625. Madera County: Thiers 23612. Nevada County: Thiers 13164. Sierra County: Thiers 13238, 21146, 23597, 23630, 23946.

Observations This species is probably the most common and widely distributed Leccinum in North America and was formerly included in the broad concept of L. aurantiacum and L. discolor. Leccinum insigne is readily distinguished by the characteristic color changes occurring in the flesh when exposed, the rust-red color of the pileus, and the absence of pigment globules in the cuticular hyphae when mounted in Melzer's. Throughout its known range it appears to be associated with aspens, which most probably accounts for its absence in the coastal forests of this state.

Edible.

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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