BOLETUS RUBRIPES Thiers, Mycologia 57:532. 1965

Illustrations: See Microfiche No. 17

Pileus 9-16 cm broad when mature, convex to obtusely convex when young, unchanging or becoming broadly convex with age; surface dry, dull, tomentose to velutinous to matted or appressed-fibrillose during all stages of development; color when young pale buff ("deep olive-buff" to "olive-buff"), unchanging or becoming pale brown ("buffy brown" to "tawny olive" to occasionally near "sayal brown" to "cinnamon") with age, sometimes fading to buff ("warm buff" to "light buff") on the margin, typically staining brown when bruised or handled; margin incurved to decurved, entire. Context up to 3 cm thick, buff to yellow ("pale olive-buff" to pale "ivory yellow" to "pale pinkish buff"), changing to blue immediately upon exposure. Taste typically unpleasant, bitter; odor often strong, unpleasant.

Tubes up to 1.5 cm in length, shallowly depressed when young, becoming broadly and deeply depressed with age; yellow ("primrose yellow" to "reed yellow") when young, changing to dark yellow ("massicot yellow" to "naphthalene yellow" to "chamois") with age, bluing immediately when bruised; pores up to 1 mm broad, angular, concolorous.

Stipe 8-13 cm long, 2-4 cm thick at the apex, equal to slightly clavate, solid, with yellow mycelium at the base; surface dry, glabrous or frequently appearing longitudinally striate, especially with age, not reticulate; color yellow ("primrose yellow") at the apex, changing to pink ("Daphne pink" to "rocellin purple") at the base, entire stipe typically becoming very dark red with age. Context yellow, dark red to almost black at the base, changing to blue when exposed.

Spore print olive brown. Spores 12.5-17.6 X 4-5 Ám, ochraceous in KOH, dark ochraceous in Melzer's, smooth, thin-walled, subcylindric to subfusoid to narrowly subellipsoid.

Basidia 26-30 X 7-13 Ám, four-spored, clavate, hyaline in KOH. Hymenial cystidia 24-35 X 5-7 Ám, scattered, embedded in the hymenium, hyaline, thin-walled, fusoid to occasionally clavate or fusoid-ventricose.

Tube trama divergent to subparallel, hyaline, staining bright ochraceous in KOH near the pores. Pileus trama interwoven, homogeneous. Pileus cuticle differentiated as a trichodermium of interwoven hyphae, brown to pale ochraceous in KOH, occasionally incrusted. Stipe cuticle bright ochraceous in KOH, differentiated as a layer of closely packed hyphal tips that are septate, relatively thick-walled, and superimposed upon a narrow layer of hyaline, interwoven hyphae that gelatinize in KOH. Clamp connections absent.

Chemical reactions KOH-context yellow orange; HNO3-context yellow orange, cuticle pink; HCl-context yellow orange; sulfoformalin-context yellow, cuticle pink; guaiac-context pale blue.

Habit, habitat, and distribution Solitary to gregarious in humus in coniferous or mixed forests. It has not been possible to determine its mycorrhizal hosts in areas at lower elevations, but hardwoods such as oaks are suspected. In the Sierra and Cascades it has been found under both pines and firs. Boletus rubripes occurs most frequently in the coastal forests in the vicinity of Mendocino. Collections have been made, however, in most of the central and northern forests of the state. Although originally described from California, it is now known from throughout the Pacific Northwest and as far away as central Mexico.

Material studied Del Norte County: Sundberg 960. Mendocino County: Largent 566; Thiers 8926, 9266, 9299, 9352, 9435, 9473, 10580, l0589, 10649, 10675, 14593, 14618, 21317. Shasta County: Thiers 12726. Sierra County: Sundberg 1460; Thiers 13203. Tuolumne County: Sundberg 286; Thiers 13277.

Observations The pale-buff to tan color of the pileus and the smooth stipe, which, when young, is yellow at the apex and red at the base, but characteristically completely changes to dark red with age, are the major distinguishing features of this species. It appears, perhaps superficially, closely related to B. calopus, but the smooth stipe and pale color of the pileus make it readily distinct. Also, the dark red stipe of the older basidiocarps is not usually seen in B. calopus. The red stipe, the absence of any reticulation on its surface, and the bitter taste make it easily distinguishable from B. appendiculatus, a species not closely related but showing some similarity in surface characters.

Edibility unknown, but if the bitter taste persists after cooking, it would not be very palatable.

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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