Taxon Profile:

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Family:

Boletaceae (Basidiomycota)

Primary Citation:

Calif. Mushrooms p. 82. 1975

Type Specimens:

Specimen 1: Isotype -- H. D. Thiers

Common Names:

Oak-loving Bolete

Description:

Latin Diagnosis: Pileus 4-10 cm latus, siccus, tomentosus vel velutinus, saepe rimosus, rufus vel rufobrunneus demum furvior vel marcidus. Contextus flavus tactu caeruleus. Sapor et odor mitis. Tubuli 1 cm longi, olivaceo-flavi tactu caerulei; pori 0.5-1 mm lati, concolores tactu caerulei. Stipes 5-8 cm longus, 1-2 cm crassus, siccus, glaber, apice flavus, rufus basim versus. Sporae 12-16.5 X 5.5-8 µm, subellipsoideae vel subfusoideae, laeves. Cystidia 25-40 X 7-12 µm, clavata. Cuticula intertexta cellulis clavatis vel vesiculosis gregatim. Holotypus (no. 18557) a H. D. Thiers lectus prope Fremont Campground, Los Padres National Forest, Santa Barbara County, January 28, 1967; in Herbarium San Francisco State University conservatus.

Description: Pileus 4-10 cm broad when mature, convex to pulvinate when young, unchanging or becoming broadly convex to plane to highly irregular and undulating with age; surface dry to slightly moist, conspicuously tomentose when young, unchanging or appearing subglabrous with age, sometimes becoming rimose to split and often developing into large cracks or conspicuous fissures; color when young near reddish brown to red ("garnet brown" to "madder brown" to "Vandyke red" to "acajou red"), sometimes overlain by an olive brown ("tawny-olive" to pale "buckthorn brown") tomentum, with age, in some the red color darkens to near dark red ("Hay's maroon" to "Vandyke red" to "diamine brown"), in others the red fades and the olive brown ("tawny-olive" to "clay color") predominates; frequently, the combination of a red background and pallid tomenturn gives the pileus a pinkish-brown appearance; margin incurved, becoming decurved, entire becoming eroded. Context 1-2 cm thick, yellow ("pale chalcedony yellow" to "sulphur yellow") with a slight reddening under the cuticle, slowly and erratically becoming blue when exposed. Taste slightly acid near the cuticle, otherwise mild; odor not distinctive.

Observations: Observations This species obviously belongs in the Subtomentosi section and also in the subsection Subtomentosi. It does not, however, satisfactorily fit the description of any species known for that taxon. It is recognized by the peculiar color combination in the pileus. The reddish color sometimes almost completely dominates, but more often the cuticle is red to rose colored when young but becomes overlain and at least partially masked with olive-brown fibrils as it gets older. The stipe is also distinctive in that it is rather short, often pinched at the base, and shows very distinct red and yellow portions. The cuticle is somewhat suggestive of that of B. chrysenteron, but the incrustations do not stain cinnamon brown as they do in that species. The colors of the pileus and stipe differentiate it from B. subtomentosus, and the absence of any blue discoloration on the pileus when ammonium hydroxide is applied precludes calling it B. spadiceus.