E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include a dry reddish brown cap, when young with a fine white bloom, white unstaining flesh, pores that are whitish at first becoming yellow or yellowish buff and finally greenish, the pores sometimes becoming cinnamon brown near cap margin, dry white-reticulate club-shaped stem that is white when young, often developing brownish tinges when old, and spring growth in the mountains. The description is derived from Arora(2). This species has been referred to as Boletus pinophilus Pilat & Dermek and as its synonym Boletus pinicola (Vittad.) A. Venturi, but that European species is considered by some authors to be somewhat different. Bessette(3) describes as "widely distributed throughout North America" a taxon under the name Boletus pinophilus Pilat & Dermek (with spores given as 15-20 x 4-6 microns). Arora(2) say that the spores of B. rex-veris are slightly narrower than those of the European Boletus pinophilus, but Snell(6) found that spores of dried collections of Boletus edulis subsp. pinicola sent to them from California, Montana, Wyoming and Colorado were somewhat wider and longer (otherwise fitting the European descriptions). Whereas the European descriptions gave the spores as 14-17 x 4.5-5.5 microns, 13-17.5 x 4.5-6 microns etc., they found the spores of the specimens on the whole slightly larger: 14-21 x 5-6 microns, with a few 7 microns wide, mostly 16-18 x 5.5-6 microns, with a tendency for the majority to vary in length directly with the size of the specimens. (Snell(6)). Nevertheless, sequencing of a Washington "spring king" indicated that it was Boletus rex-veris (M. Beug, pers. comm.).

Collections were examined from CA and OR by Arora(2). In CA it is locally abundant in the mountains, fruiting in April-June at mid-elevations (3000-4000 feet) and into July at higher elevations (up to 7000 feet), occurring at somewhat lower elevations in Cascades of OR and WA, extending east through the Blue Mountains to ID and perhaps beyond, and north to BC, outside of California also fruiting principally in spring or early summer, (Arora(2)).

Cap:
10-30cm across or occasionally larger, broadly convex or bun-shaped, becoming nearly flat or uneven; usually reddish brown but varying to tan or paler where hidden by soil or humus and often developing ocher tones when old or where exposed to the sun, and at other times dark dull brown; typically not viscid except when wet or when old, bald "except for a very fine white bloom that covers often irregular areas of the young cap"

Flesh:
firm; white in both cap and stem (or reddish-tinged just above tube layer), unchanging when cut

Pores:
pores and tube layer "white when young, gradually becoming yellow or yellowish-buff and finally olive-yellow or greenish", pores near the cap margin may become cinnamon brown, but pore surface not becoming uniformly brown or cinnamon

Stem:
5-20cm or more long, 2.5-10cm wide, typically club-shaped with a pointed and often a curved base when young, becoming more or less equal when old "but usually retaining a tapered or pointed base"; white when young, often developing tan or more often reddish brown tinges when old, especially in the upper part but occasionally throughout; typically reticulate over upper part, reticulum fine and white when young (sometimes barely discernable), often brown when old "as the meshes become wider and coarser"

Microscopic:
spores (14)15-17(19) x (4)4.5-5(5.2) microns, elliptic-subfusiform with prominent suprahilar depression, yellowish; basidia 4-spored, (40)45-60(65) x 9-11.5 microns, clavate; pleurocystidia (45)50-65 x 6.5-7.5 microns, cylindric-fusiform, colorless, cheilocystidia (30)45-70 x 11-17 microns, "clavate, sometimes narrowing or with capitulum or wide-fusiform"; cap cuticle an interwoven trichoderm, often weakly gelatinized when old but typically not gelatinized when young, made up of chains of cells with cylindric end cells having sharpened or rounded tips, (20)30-80(128) x (6.5)8-14(20) microns

Spore Deposit:
olive-brown