SUILLUS VOLCANALIS Thiers, Madrono 19:158. 1967

Illustrations: See Microfiche No. 51

Pileus 9-12 cm broad when mature, convex to irregular when young, becoming plano-convex to highly irregular with an undulating margin to plane with an uplifted margin when older; surface often irregularly pitted, appearing closely appressed fibrillose to streaked, viscid; color when young yellow ("primrose yellow") with numerous buff-colored areas ("ochraceous-buff" to "ochraceous-tawny"), when older frequently with some areas remaining yellow ("picric yellow") and others reddish brown ("vinaceous rufous"), or in some basidiocarps the background yellow to tan ("antimony yellow" to "warm buff") with irregular areas colored pinkish ("testaceous"), when very old red ("russet" to "tawny") with paler yellowish areas intermixed; margin strongly incurved when young, usually with a white to pallid, conspicuous roll of partial-veil tissue attached, becoming decurved and glabrous with age. Context 1-2 cm thick, white to pale yellow ("ivory yellow") when young, typically becoming bright yellow ("massicot yellow") in older pilei, unchanging when exposed. Taste and odor not distinctive.

Tubes 1-1.5 cm long, shallowly to deeply depressed during all stages of development, when young bright yellow ("straw yellow"), becoming dark yellow ("aniline yellow") when older, unchanging when exposed; pores less than 1 mm broad, angular, concolorous with tubes, unchanging when bruised.

Stipe 3-6 cm long, 1.5-3 cm thick at apex, equal to occasionally somewhat ventricose to flared at the base, solid; surface dry, appearing glabrous to smooth, glandulae apparent at least in the apex when very old; color when young white, except pale yellow at the apex, when older becoming dark yellow ("massicot yellow") at the apex, and brown to rust colored ("buckthorn brown" to "ochraceous-tawny" to "tawny") toward the base; no annulus. Context white when young, yellowish with age, unchanging when exposed.

Spore print brown. Spores 6.6-10 X 3-4 Ám, cylindric to subellipsoid, ventricose in side view, hyaline in KOH, pale yellow in Melzer's, smooth, thin-walled.

Basidia 25-31 X 7-11 Ám, hyaline in KOH, clavate, four-spored. Hymenial cystidia 24-47 X 5-8 Ám, rare to absent along sides of tubes, scattered to relatively abundant on pores, fascicled, no solitary cystidia seen, dark brown in KOH, thin-walled, bases of many appearing incrusted, cylindric to subclavate, rust brown ("ochraceous-tawny") in Melzer's.

Tube trama hyaline, divergent from a distinct mediostratum, appearing subgelatinous in KOH, hyphae 3-5 Ám wide. Pileus trama with a compactly interwoven layer near tubes, which stains dark brown in KOH, surmounted by a layer of loosely interwoven, more or less homogeneous hyphae. Pileus cuticle composed of a narrow ixotrichodermium with hyphae that appear to be heavily incrusted and stain dark brown in KOH, surmounting a broad layer of interwoven hyphae 5-6 Ám wide. Stipe cuticle interwoven, subgelatinous in KOH with occasional clusters of caulocystidia similar to those in the hymenium. Clamp connections not seen.

Chemical reactions unknown.

Habit, habitat, and distribution Gregarious to scattered (often buried) in cinders and humus under Jeffrey pine. This species was found by uncovering "humps" of soil or cinders in the vicinity of Butte Lake and the Cinder Cone in Lassen Volcanic National Park. This is one of the very few boletes that forms basidiocarps during the summer months.

Material studied Lassen County: Thiers 12777, 12800, 12915, 12930, 12931.

Observations Because of the general stature of the basidiocarp and the absence of glandulae on the stipe, S. volcanalis appears most closely related to S. brevipes. However, S. volcanalis can be distinguished by the well-developed, noticeable cottony margin of fibrillose tissue, the yellow to tawny color of the pileus, which often appears distinctly fibrillose rather than glabrous, the longer and broader spores, and the darkening of the stipe with age.

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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