Porphyrellus pseudoscaber: The Ultimate Mushroom Guide
About The Porphyrellus pseudoscaber Mushroom
Porphyrellus porphyrosporus is a rare fungus belonging to the family Boletaceae. With its purple-brown cap and stem, P. porphyrosporus is not easy to spot, despite its large size. This species occurs under pines, but can also be found beneath deciduous trees. It is a large (both cap diameter and stem length up to 15 cm) brown bolete. Its most distinctive features are the purple-brown spore print and the blue-green color of the flesh at the top of the stem and above the hymenium.
This is a widespread species of Europe, especially in the north, but is nowhere particularly common. The fruit bodies appear from late summer to autumn, often in small groups, associated with broad-leaved trees such as beech and oak.
DNA testing moved this mushroom into the newly erected genus “Porphyrellus.” There is an ongoing name debate between porphyrosporus and pseudoscaber. At one time they were thought to be two lookalike species with porphyrosporus growing under deciduous trees and having flesh that stains, versus pseudoscaber that grew under conifers with cap flesh that DNS.
Tylopilus pseudoscaber (Secretan) Smith and Thiers, Boletes of Michigan, p.96. 1971
Boletus pseudoscaber Secretan, Mycogr. Suisse 3:13. 1833.
Boletus olivaceobrunneus Zeller and Bailey, Mycologia 27:457. 1935.
Porphyrellus atrofuscus Dick and Snell, Mycologia 52:449. 1960.
Other names: Dusky Bolete.
Porphyrellus pseudoscaber Identification
6-15 cm broad at maturity, convex to broadly convex when young, becoming plano-convex to irregular with an undulating to uneven margin with age; surface dull, unpolished, velutinous to tomentose during all stages of development, smooth, rarely finely areolate and fibrillose-scaly; color sooty black to very dark brown ("clove brown" to "fuscous" to "mummy brown"), occasionally slightly darker on the disc and paler on the margin, black when dried; margin entire, incurved to decurved. Context 1-2 cm thick, white, slowly staining weakly blue in some areas, pink ("testaceous") in other areas, blue discoloration slowly disappearing and becoming pink ("testaceous"), staining wax paper dark blue-green. Taste is not distinctive; odor is often strong and pungent.
1.5-2 cm long, shorter toward the margin, deeply and broadly to narrowly depressed, dark brown to almost black ("cinnamon-drab" to "drab" to "benzo brown"), slightly paler on the margin, staining blue at first when bruised, then changing to purplish-brown ("deep brownish drab" to "dusky drab"); pores up to 1 mm wide with occasional larger pores irregularly distributed, angular, concolorous with the tubes, frequently bluing and then changing to dark mahogany brown when bruised.
13-20 cm long, 1.5-2 cm thick at the apex, clavate to subclavate, solid to stuffed; surface dry, dull, glabrous, longitudinally ridged and often somewhat reticulate, dark brown ("bone brown" to "clove brown"), staining reddish vinaceous when first bruised, eventually becoming dark brown to black, occasionally scattered areas staining blue, whitish at the base. Context pale pinkish-tan ("pale pinkish buff"), becoming pale flesh color ("testaceous") when exposed.
13.8-17.6 X 6-9.6 ľm, dark ochraceous in Melzer's, pale yellow in KOH, smooth, thick-walled, subfusoid to subcylindric to subovoid in face view, inequilateral in side view, no apical pore.
30-45 X 10-15 ľm, clavate, four-spored, hyaline; irregular areas in hymenium staining dark brown in KOH. Hymenial cystidia 36-51 X I2-15 ľm, abundant, cinnamon brown in KOH, chocolate brown in Melzer's, embedded in the hymenium, fusoid-ventricose to mucronate to clavate with elongated, tapering apices.
Trama divergent, hyaline, appearing somewhat gelatinous in KOH, hyphae ą8 um wide. Pileus trama interwoven, hyaline except for scattered areas that stain brown in KOH, homogeneous. Pileus cuticle differentiated as a trichodermium, which frequently collapses with age, with scattered free hyphal tips colored cinnamon-brown in KOH, not incrusted, contents of cells staining brown in KOH, hyphae up to 10 ľm wide. Stipe cuticle is differentiated as a tangled trichodermium that stains cinnamon-brown in KOH. Clamp connections absent.
KOH-cuticle dark red, context red; HN03, HCL, and H2SO4-context pink, cuticle bright red; sulfoformalin-context and cuticle red; FeS04-cuticle dark gray.
Habitat and Distribution
Scattered in the mixed coastal forests of northern California. It is often found growing on well-decomposed Sitka spruce logs and stumps but has also been found in humus under Sitka spruce and various pines. Fruiting during the fall and winter season. Usually much more abundant in the area north of Eureka than elsewhere in the state.
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