GASTROBOLETUS SUILLOIDES Thiers, Brittonia 21:248. 1969
Gastrocarp 2.5-5 cm broad at maturity, convex to subglobose to plano-convex during all stages of development; surface dry, glabrous when young, often becoming fibrillose to tomentose to appressed fibrillose-scaly with age, sometimes becoming areolate with age; color light brown ("ochraceous-buff" to "cinnamon-brown" to "buckthorn brown") to occasionally brown to dark brown ("mikado brown" to "sayal brown") when older, unchanging when bruised. Context 3-7 mm thick, buff to yellow ("ochraceous-buff" to pale "cream color"), unchanging when exposed. Taste and odor not distinctive.
Gleba distinctly tubulose, tubes arranged so as to make a spore deposit impossible, typically exposed at maturity, greenish yellow to olive yellow, unchanging when bruised or exposed; pores small, irregular, concolorous with the tubes.
Stipe-columella typically poorly developed, 5-10 mm long, 3-5 mm thick, surface dry, tomentose to appressed-fibrillose, more or less concolorous with the pileus during all stages of development.
Spores 6.4-12 X 3.5-4.5 Ám, brown to dark brown in KOH and Melzer's, ellipsoid to inequilateral, some appearing ovoid or occasionally more or less constricted at the midportion, smooth, walls slightly thickened, sterigmal appendages oblique.
Basidia 20-37 X 6-8 Ám, narrowly clavate to subcylindric, clavate to depressed at the center, hyaline in KOH, with four sterigmata. Hymenial cystidia 35-55 X 5-11 Ám, abundant to numerous, typically clustered, and staining dark brown in KOH and Melzer's (as in Suillus), clavate to cylindric to subcylindric.
Tube trama divergent from a distinct central strand, hyphae 4-9 Ám broad. Peridial trama interwoven, hyphae 5-30 Ám broad, staining bright ochraceous in KOH, deep orange in Melzer's. Peridial cuticle appressed, of interwoven to subparallel to sometimes tangled hyphae, 5-12 Ám broad, yellow to dark brown in KOH and Melzer's, not gelatinous. Cuticle of stipe-columella composed of loosely subparallel hyphae 7-30 Ám broad and having some inflated cells up to 50 Ám broad, grayish yellow in KOH. Clamp connections absent.
Habit, habitat, and distribution Solitary to gregarious, hypogeous to partially emergent, under conifers, including red fir and lodgepole pine. Known only from higher elevations in the Sierra Nevada of California in late summer.
Material studied Fresno County: Thiers 13412. Inyo County: Thiers 20990. Tehama County: Cooke 38731.
Observations This species shows close affinity with the genus Suillus because of the presence of fascicled cystidia that darken in KOH. This relationship is further substantiated by the similarity of shape and size of the spores of the two taxa. However, neither a viscid pellicle nor an annulus was observed in any collections of G. suilloides.
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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