BOLETUS REGIUS Krombholz, Naturg. Abb. Schw. 2:3. 1832
Boletus appendiculatus var. regius (Krombholz) Konrad, Bull. Soc. Mycol. Fr. 41:63. 1925.
Boletus appendiculatus ssp. regius (Krombholz) Quelet, Enchir. Fung. p. 160. 1886.
Illustrations: See Microfiche No. 16
Kawamura, S., Icones of Japanese Fungi, pl. 240.
Leclair, A., and H. Essette, Les Bolets, pl. 40.
Romagnesi, H., Nouvel Atlas des Champignons, pl. 126B.
Singer, R., Die Rohrlinge, Teil II, pl. VII, figs. 8-9; pl. IX, figs. 6-10.

Pileus 8-20 cm broad when mature, convex to broadly convex when young, unchanging or becoming plano-convex to highly irregular in outline with age, typically very massive; surface dry to moist, tomentose to velutinous when young, unchanging or becoming glabrous with age, sometimes highly uneven and conspicuously pitted during all stages of development; color bright pink to rose pink ("Eugenia red" to "jasper red" to "acajou red" to "Pompeian red") during all stages of development, occasionally with brown ("sayal brown") areas when young, and frequently becoming somewhat yellowish toward the margin with age; margin entire, incurved when young, becoming decurved with age. Context 1.5-4.5 cm thick, intense yellow ("barium yellow" to "citron yellow" to "picric yellow"), slowly and incompletely changing to blue in spots or irregular areas when exposed. Taste and odor not distinctive.

Tubes 1-2.5 cm long, adnexed when young, becoming deeply and broadly depressed with age, bright yellow ("citron yellow") when young, unchanging or becoming deeper yellow ("empire yellow" to "pinard yellow" to "picric yellow") with age, bluing when exposed; pores 0.5-1 mm broad, angular, concolorous with tubes, bluing when bruised.

Stipe 7-11.5 cm long, 3-5 cm thick at the apex, usually conspicuously bulbous, sometimes clavate-bulbous or abruptly bulbous to ventricose, solid; surface dry, finely but distinctly reticulate for two thirds of or entire length, bright yellow ("picric yellow" to "pinard yellow" to "empire yellow"), reticulations concolorous with the surface. Context yellow in cortical region, changing to whitish or pallid in center, reddish to pale vinaceous ("avellaneous") at the base, unchanging when exposed.

Spore print pale olive brown to olive brown. Spores 12.5-16.5 X 3.7-5 Ám ochraceous in Melzer's, pale ochraceous to hyaline in KOH, ellipsoid to fusoid to subcylindric, smooth, thin-walled.

Basidia 27-32 X 7-9 Ám, clavate, hyaline, four-spored. Hymenial cystidia 25-45 X 8-17 Ám, scattered to numerous, more abundant on the pores, hyaline, thin-walled, clavate to fusoid to subcylindric. Hymenium very pale yellow in KOH with occasional yellow amorphous masses interspersed.

Tube trama strongly divergent from a distinct central strand, hyaline. Pileus trama interwoven, homogeneous. Pileus cuticle differentiated as a trichodermium of tangled to somewhat repent hyphae with free, more or less erect hyphal tips, appearing amyloid. Hypodermium appearing gelatinous in KOH. Stipe cuticle differentiated as a layer of fertile basidia and hymeniform to vesiculose cells with interspersed caulocystidia similar to the hymenial cystidia. Clamp connections absent.

Chemical reactions HNO3-context pink to pale vinaceous; FeSO4context gray, cuticle pale lavender.

Habit, habitat, and distribution Solitary to scattered in soil in mixed forests in the coastal regions and under firs at higher elevations. In the coastal forests and other areas at lower elevations, it is usually associated with oaks, but in the absence of this host in the mountains it apparently enters into associations with conifers, especially firs. Fruiting in late August and September in the Sierra Nevada and Cascades; during the fall rainy season along the coast. It is sometimes abundant in the Santa Cruz Peninsula but usually infrequent to rare elsewhere.

Material studied Marin County: Hitsch 12-1-69. Mendocino County: Thiers 9408, 10592, 21418. San Mateo County: Sundberg 391; Thiers 18190, 18337, 26928, 26954, 26979. Santa Cruz County: Malloch 360; Thiers 18552. Shasta County: Thiers 21590. Siskiyou County: Thiers 25382. Sonoma County: Dusatko 10; Thiers 9411. Tuolumne County: Thiers 11226, 12637.

Observations The deep-old-rose to pale-pink pileus, which with age may fade to almost yellow with only pinkish spots or flushes, the yellow context that only erratically changes to blue when exposed, the bright-yellow, noticeably reticulate stipe, and spores 3.5-5.5 Ám broad are the distinguishing features of this species. Boletus regius is apparently most closely related to B. speciosus, but that species has not yet been found in western North America. Boletus speciosus has wider spores, a more elongated stipe, and the flesh turns blue immediately when exposed.

In California B. regius is most closely related to B. appendiculatus and is often confused with it. The ochraceous to rust or rust-brown color of the pileus of B. appendiculatus is the major character separating them. Both species occupy the same type of habitat and, at least in the San Francisco Bay Area, there seems to be considerable intergradation.

Edible, but not considered of high quality.

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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