SUILLUS FUSCOTOMENTOSUS Thiers and Smith, Contr. Toward a Monogr. of N. Am. Sp. of Suillus, p. 65. 1964

Illustrations: See Microfiche No. 41

Pileus 3.5-15 cm broad when mature, when young subconic to convex to obtusely convex, becoming broadly convex to plano-convex, occasionally highly irregular in shape with undulating margin; surface moist to subviscid with age, conspicuously fibrillose to fibrillose-scaly to almost squamulose when young, fibrils often becoming agglutinated at the tips, sometimes becoming less dense with age and appearing appressed, occasionally appearing glabrous when very old; color when young olive brown to near fuscous ("clove brown" to "bone brown" to "fuscous") on the disc, unchanging or fading slightly toward the margin, with age slowly fading to dark vinaceous brown ("rood's brown" to "Vandyke brown" to "Verona brown" to "warm sepia"), eventually becoming near cinnamon ("clay color" to "tawny-olive" to "cinnamon" to "sayal brown"), occasionally remaining dark brown ("Verona brown") on the disc and fading to pinkish brown ("cinnamon" to "avellaneous") on the margin, fibrils more or less concolorous or darker than the surface; margin entire, glabrous, no evidence of partial veil during any stage of development. Context 1-2 cm thick on the disc, yellow ("ivory yellow" to "cartridge buff") in young pilei, changing to deep yellow ("primrose yellow" to "cream color" to "naphthalene yellow") when older, unchanging when exposed. Taste not distinctive to weakly acid and unpleasant; odor not distinctive.

Tubes up to 1.5 cm long, adnate to shallowly and narrowly depressed around the stipe, unchanging or becoming subdecurrent to broadly shallowly depressed with age; when young pale yellow ("deep colonial buff" to "colonial buff" to "deep olive-buff"), changing to yellow to buff ("antimony yellow" to "warm buff"), finally becoming olive yellow ("Isabella color" to "chamois" to .'old gold" to "olive lake"), unchanging when exposed; pores up to 1 mm broad, angular, concolorous, unchanging when bruised.

Stipe 4-10 cm long, 1-3 cm thick at apex, equal to typically obscurely clavate to clavate, with white to pale lavender ("avellaneous") mycelium at the base, solid; surface strongly and often noticeably punctate, glandulae relatively large and often becoming elongated with age, more or less concolorous with surface, darkening when handled, moist but not viscid; color when young yellow ("Naples yellow" to "mustard yellow"), typically becoming pallid ("pale olive-buff" to "warm buff"), sometimes becoming bright yellow ("amber yellow" to "strontian yellow") at the apex, occasionally becoming pinkish ("pale pinkish buff") particularly at the base, unchanging upon bruising; no evidence of an annulus. Context concolorous with surface, unchanging when exposed.

Spore print olive brown. Spores 9-12 X 3-4 µm, smooth, thin-walled, fusoid to subellipsoid to subcylindric in face view, slightly inequilateral in profile, pale yellow in KOH, pale ochraceous in Melzer's.

Basidia 21-24 X 6-8 µm, apparently two- and four-spored, hyaline, clavate. Hymenial cystidia 30-45 X 8-10 µm, cylindric to subclavate to obtusely fusoid to highly irregular in outline, in clusters, rare to absent on sides of tubes, abundant on the pores; typically staining dark brown to black in KOH, and appearing incrusted near the pores, often only basal portion of cluster staining when located on side of tubes.

Tube trama hyaline, subgelatinous in KOH, divergent, hyphae ±5 µm wide. Pileus trama interwoven, homogeneous. Pileus cuticle differentiated as a highly uneven trichodermium of more or less erect, septate hyphal tips, not at all or only slightly gelatinous in KOH, hyphae typically appearing incrusted, and staining pale brown in KOH, cells ±7 µm wide. Stipe cuticle not gelatinous in KOH, with numerous large clusters of caulocystidia 60-90 X 6-10 µm, which stain dark vinaceous to black in KOH, cylindric to highly irregular in outline. Clamp connections not seen.

Chemical reactions NH₄OH-context gray; HNO₃ and HCl-cuticle yellow, context and tubes lavender; H₂SO₄-cuticle, context, and tubes yellow; FeSO₄-context gray.

Habit, habitat, and distribution Solitary to gregarious to occasionally cespitose in soil under ponderosa pine. Originally described from collections made in Santa Cruz County, this species has now been found up to elevations of 3,000 to 4,000 feet in the Sierra foothills and at similar elevations in Castle Crags State Park and vicinity in the Cascade Range. Although often seen in mixed forests, no fruitings have ever been encountered in areas where ponderosa pines were not a conspicuous component of the forest cover. It is often abundant in the fall and winter fruiting season, particularly in the Castle Crags area.

Material studied Butte County: Ripley 1613. Santa Cruz County: Sundberg 178, 211; Thiers 10622, 10623, 10759, 10794, 10981. Shasta County: Thiers 18219, 18220, 18714, 21597, 21622, 21679, 23087. Tuolumne County: Thiers 18618.

Observations This is a very distinctive and easily recognized species. Its most characteristic features are the dark-colored fibrils on the surface of the pileus, the moist to only subviscid cuticle, the unchanging context, and the apparent association with only ponderosa pine. Suillus fuscotomentosus appears rather closely related to S. californicus, but that species is so poorly known that no definitive comparisons can be made. Suillus fuscotomentosus is also somewhat similar in appearance to the dark forms of S. acerbus, but that species has a distinctly viscid pileus, the cuticle is differently organized, and it is associated, so far as is know, only with Monterey pine. Suillus tomentosus, another species with a conspicuously fibrillose cuticle, is easily distinguished by the much paler color of the pileus and the blue discoloration of the context when bruised or exposed.

This species is not poisonous, but is rated very low as an esculent because of the insipid taste and unpleasing texture of the cooked flesh.