SUILLUS UMBONATUS Dick and Snell, Mycologia 52:446. 1960

Illustrations: See Microfiche No. 50
Smith, A. H., Mushroom Hunter's Field Guide, p. 85, pl. 51.
Smith, A. H., and H. D. Thiers, A Contribution Toward a Monograph of North American Species of Suillus, pls. 29-31.
Snell, W. H., and E. A. Dick, The Boleti of Northeastern North America, pl. 20.

Pileus 4-10 cm broad, convex to acutely convex when young, becoming broadly convex to umbonate to plane when older, occasionally becoming highly irregular and undulating with age; surface viscid, often appearing conspicuously streaked with age, often with spots or flecks on the margin; background color tan to pale yellow ("cream-buff" to "chamois" to "warm buff" to "ochraceous-buff"), sometimes somewhat darker, unchanging or becoming darker with age, occasionally dull pinkish brown ("avellaneous") to olivaceous near the margin, plaques concolorous or often reddish brown ("ochraceous-tawny" to "tawny" to "russet"); margin incurved and attached to stipe by partial veil when young, becoming appendiculate as cap expands, but usually glabrous at maturity. Context 1-2 cm thick, pale yellow ("cream color" to "massicot yellow") in young basidiocarps, not changing or becoming pale olive buff with age, changing to pinkish brown ("avellaneous") upon exposure. Taste unpleasant but not acid; odor mild.

Tubes up to 1 cm long when young deep yellow ("Mustard yellow" to "amber yellow"), becoming dark yellow ("primuline yellow" to "old gold") with age, unchanging or rarely with rust-colored ("ochraceous-tawny" stains when bruised; pores 2-3 mm long, 1 mm broad, radially arranged, compound, concolorous with tubes.

Stipe 3-7 cm long, 0.5-1 cm thick at the apex, equal or slightly enlarged or tapering toward the base, white mycelium at the base, solid; surface moist to subviscid, tan ("warm buff") above the annulus, unchanging or becoming pallid ("pale olive-buff") toward the base, often staining brown when handled; glandulae not apparent on the surface when young, but usually apparent and yellow brown to brown with age; annulus viscid, pallid ("pinkish cinnamon"), subapical but sometimes appearing subperonate. Context pale yellow, unchanging or when young changing to pale lavender ("avellaneous").

Spore print olive brown. Spores 7-11 X 3.5-4.5 Ám, pale ochraceous in Melzer's and KOH, smooth, thin-waled, ellipsoid to subfusoid, obscurely ventricose in side view.

Basidia 20-25 X 6-8 Ám, hyaline, four-spored, clavate. Hymenial cystidia 25-40 X 6-10 Ám, in clusters, hyaline but staining dark brown in KOH, scattered to numerous, cylindric to clavate.

Tube trama gelatinous in KOH, divergent, hyaline. Pileus trama interwoven, homogeneous. Pileus cuticle differentiated as an ixotrichodermium, hyphae 3-6 Ám wide. Caulocystidia similar to hymenial cystidia. Clamp connections absent.

Chemical reactions unknown.

Habit, habitat, and distribution Gregarious to cespitose in soil under lodgepole and beach pine. Collections of this species have been made almost annually in Jackson State Forest in Mendocino County where the basidiocarps appear among Bishop and beach pine mixed with tanbark oak and other hardwoods. In the Sierra Nevada and Cascade ranges it has been found only in forests composed of lodgepole pine, fir, and alder. Since lodgepole pine and its close relative, beach pine, are common to both habitats, it is assumed that this fungus forms mycorrhizal associations with these conifers.

Material studied El Dorado County: Thiers 20765, 20816, 20833. Humboldt County: Thiers 17612, 21381. Mendocino County: Thiers 8779, 8949, 9291, 9345, 9723, 11075, 14612, 21324. Sierra County: Thiers 13161, 13201, 13202, 13210, 21131, 21132, 21141.

Observations Suillus umbonatus is characterized by the presence of a distinct, viscid annulus that is colored pale watery brown, and by the development of olivaceous tones in the pileus with age; it is further distinguished by the failure of the context of the stipe base to become vinaceous when exposed. As has already been pointed out, there is considerable confusion surrounding this species and its relationship with S. sibiricus and S. americanus. Suillus americanus, apparently not present in this state, does not have the noticeably viscid annulus, has a differently colored pileus, and develops reddish scales or plaques on the pileus with age. Suillus sibiricus can be distinguished by the absence of an annulus, the much brighter and more intensely yellow pileus, and the vinaceous discoloration of the context of the base of the stipe.

Edibility not determined.

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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