BOLETUS EDULIS Fries, Syst. Mycol. 1:392. 1821
Leccinum Edule (Fries) S. F. Gray, Nat. Arr. Brit. Pls. 1:647. 1821.
Tubiporus edulis (Fries) Karsten, Rev. Mycol. 3:16. 1881.
Dictyopus edulis (Fries) Quélet, Enchir. Fung., p. 159. 1886.
Ceriomyces crassus Murrill, Mycologia 1:149. 1909.
Boletus crassus (Murrill) Jaczewski,Opred. Grib. 1:594. 1913.
Illustrations: See Microfiche No. 8
Kawamura, S., Icones of Japanese Fungi, p1. 239.
Lange, J. E., and M. Lange, 600 Pilze in Farben, p. 191.
Leclair, A., and H. Essette, Les Bolets, p1. 34.
Romagnesi, H., Nouvel Atlas des Champignons, pl. 272.
Singer, R., Die Rohrlinge, Teil II, pl. II, figs. 1-9; pl. III, figs. 1-6; p1. IV, figs. 1-5.
Smith, A. H., The Mushroom Hunter's Field Guide, p. 96, p1. 61.
Smith, A. H., Mushrooms in Their Natural Habitats, Reel V.
Smith, A. H., and H. D. Thiers, The Boletes of Michigan, pls. 14, 147.
Snell, W. H., and E. A. Dick, The Boleti of Northeastern North America, pl. 32.

Pileus 9-18 cm broad when mature, convex to obtusely convex when young, becoming broadly convex to plano-convex at maturity, typically very massive and heavy; surface moist to lubricous, usually becoming viscid to subviscid when wet or with age, uneven to frequently becoming irregularly pitted or wrinkled with age; color when young pale brown to buff ("warm buff" to "ochraceous buff" to "antimony yellow" to "chamois"), with age darkening to brown to reddish brown ("cinnamon brown" to "Mikado brown" to "tawny"), marginal portion often paler than the disc; margin entire, incurved when young, becoming decurved when older. Context 2-4 cm thick, firm, white except concolorous with cuticle adjacent to it, unchanging or darkening slightly when exposed. Taste and odor mild.

Tubes 1-3 cm long, adnexed, becoming depressed with age, typically stuffed when young; white when young, becoming yellow ("reed yellow" to "olive-yellow" to "citron green") with age, unchanging when exposed; pores very small, two to three per millimeter, angular, concolorous with tubes, unchanging or staining brown when bruised.

Stipe 8-16 cm long, 1.5-2.5 cm thick at the apex, massive, usually conspicuously clavate, up to 6 cm thick at bulbous base, solid, white tomentum at the base; surface dry to moist; white to occasionally pale brown ("cinnamon" to "pinkish cinnamon"), glabrous, reticulate at least over some portion, reticulations sometimes apparent only in apical region with basal portion only uneven or wrinkled. Context white, unchanging except for occasional brown stain at the base.

Spore print dark olive brown. Spores 13-18 X 4-7 µm, fusiform to subellipsoid, inequilateral in side view, hyaline to pale ochraceous in KOH, dark ochraceous in Melzer's, smooth, walls slightly thickened.

Basidia 30-40 X 10-12 µm, hyaline, clavate, four-spored. Hymenial cystidia 48-67 X 5-10 µm, often inconspicuous, hyaline, thin-walled, often deeply embedded in the hymenium, fusoid-ventricose, often narrowed and with tapered, elongated apices.

Tube trama hyaline in KOH, obscurely divergent to subparallel, hyphae 4-7 µm wide. Pileus trama homogeneous, loosely interwoven, hyaline, hyphae 5-7 µm wide. Pileus cuticle differentiated as a tangled trichodermium, which collapses with age, occasional free hyphal tips; hyphae 5-7 µm wide. Stipe cuticle differentiated as a layer of fertile basidia with scattered-to-numerous fusoid-ventricose caulocystidia. Clamp connections absent.

Chemical reactions KOH -context pale brown; NH4OH -context red to dark pink.

Habit, habitat, and distribution Solitary to gregarious in soil in the pine forests over most of California. Fruiting shortly after the onset of the rainy season or after thunderstorms in the mountains. There is little doubt that this species is distributed throughout the state, although no collections have been examined from the southern portion. Generally B. edulis is found associated with either coastal or montane species of pines; however, there are some varieties that form mycorrhizal associations with various hardwoods, and this type of habitat should not be overlooked. It is one of our most common species.

Material studied Amador County: Thiers 16924. Butte County: Collett 20; Ripley 1640. Calaveras County: Thiers 16537. Del Norte County: Thiers 17644. Fresno County: Thiers 13372. Humboldt County: Largent 438; Thiers 13984, 14094, 14489, 22887. Lassen County: Thiers 12788. Madera County: Thiers 20906. Marin County: Shervanick 381. Mariposa County: Thiers 20975. Mendocino County: Peters 72; Thiers 8155, 8780, 8851, 9285, 9288, 9340, 10571, 10596, 10646, 11849. Monterey County: Thiers 9416. San Francisco County: Motta 4; Peters 494. San Mateo County: Thiers 11966, 18060. Santa Cruz County: Thiers 10750. Shasta County: Thiers 21588. Sierra County: Thiers 13227. Siskiyou County: Thiers 23492. Sonoma County: Thiers 9414. Trinity County: Thiers 9386. Tuolumne County: Orr 1314; Thiers 12623, 16973, 19638.

Observations This well-known species needs little comment. The basidiocarps are recognized by the yellow-brown to brown, slightly viscid pileus, the white, stuffed tubes, which become yellow with maturity, and the rather massive, often clavate stipe that is reticulated at least at the apex. Numerous subspecies, varieties and forms have been described; however, most of these occur in other countries and are of no concern here. Snell has indicated that ssp. pinicola is present in California, and it may be the common form encountered. Until a more thorough and critical study has been done, none of the taxa below the rank of species will be indicated.

In the coastal forests of the northern part of the state B. fibrillosus might be confused with B. edulis. However, B. fibrillosus has a dry, much darker colored, fibrillose pileus, yellow tubes when young, and a much darker stipe. Another species more likely to be confused with B. edulis is B. aereus, which forms mycorrhizal associations with oak and possibly other hardwoods. Boletus aereus is distinguished macroscopically by the very dark color of its glabrous pileus; microscopically, the pileus cuticle is nongelatinous when mounted in KOH. Boletus mottii is also similar to B. edulis, but is distinguished by a strongly reticulated pileus surface.

The edibility of this bolete is well known to all interested in eating mushrooms for it ranks among the best and is considered excellent in either the fresh or dried state. Unfortunately, fly larvae are often rather common in the inner tissues, which should be carefully checked.

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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