Major Groups > Boletes > "Boletus" | Red-Capped, Blue Staining > Boletus pseudosensibilis

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Boletus pseudosensibilis

[ Basidiomycota > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

This frequently misidentified eastern North American bolete is associated primarily with oaks, in upland hardwood forests. It features a red to reddish brown cap, a blue staining pore surface, and a distinctive stem that is mostly yellow, flushed with red over the bottom portion. When fresh the stem bruises moderately bluish where handled, and this helps separate it from two look-alikes, Boletus sensibilis, with a stem that bruises very blue, and Boletus bicolor, with a stem that does not bruise or, rarely, bruises very faintly. Additionally, Boletus pseudosensibilis has a cap that flashes blue to green with a drop of ammonia, along with distinctive pileipellis elements (see below).

See the key to red-capped, blue-staining boletes and the printable comparison table for three often-confused boletes for further discussion and help with identification.

Description:

Ecology: Mycorrhizal with oaks, and possibly with other hardwoods; growing scattered, or gregariously; summer and fall; widely distributed in eastern North America. The illustrated and described collections are from Illinois.

Cap: 4-16 cm; convex, becoming broadly convex; dry; finely velvety when young but soon bald; red to reddish brown or pinkish brown (most commonly reddish brown), fading to pinkish tan; when young sometimes bruising grayish where rubbed; the margin at first tucked under.

Pore Surface: Bright yellow when young, maturing to dirty orangish olive; when very young not bruising, or bruising only faintly, but soon bruising promptly blue, then slowly brown; with 1-2 circular to angular pores per mm at maturity; tubes shallow, 4-8 mm deep (rarely to 10 mm deep, in very large caps).

Stem: 6-10 cm long; 1-2.5 cm thick; usually tapered at the base; dry; solid; bald; yellow overall, with reddish tinges developing in the bottom half; bruising light blue where handled (then, over time, slowly brownish); not reticulate; basal mycelium pale to dark yellow, or sometimes whitish.

Flesh: Yellow in the cap; deep yellow or sometimes reddish in the stem; staining blue on exposure--sometimes faintly and erratically (staining usually more pronounced on older specimens).

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia flashing purplish blue to blue-green, then resolving to negative, grayish, or orangish on cap surface; negative on flesh. KOH reddish to dull orange or negative on cap surface; orangish on flesh. Iron salts grayish on cap; grayish or negative on flesh.

Spore Print: Dull olive brown.

Microscopic Features: Spores 9-12.5 x 3.5-4.5 µ; subfusoid; smooth; orangish brown to golden in KOH; brownish in Melzer's. Hymenial cystidia fusoid-ventricose; 20-35 x 5-10 µ; hyaline or with orangish contents in KOH. Pileipellis a collapsing trichoderm of elements 5-12.5 (-15) µ wide, smooth, hyaline to ochraceous or golden in KOH; at first with primarily tubular terminal cells, but by maturity developing many subterminal and terminal cells that are septate at short intervals, with terminal cell tubular or obnapiform.

REFERENCES: Smith & Thiers, 1971. (Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Bessette, Roody & Bessette, 2000; Roody, 2003; Kuo & Methven, 2014.) Herb. Kuo 07250304, 08210501, 07300701, 07231001, 09031401.

My assessment of the pileipellis of this species disagrees in part with that of Smith & Thiers (1971), who describe it as a "cutis" that is "never a trichoderm"; in my collections the youngest caps manifest a trichoderm, which soon collapses and then appears like a cutis. Additionally, the young terminal elements in my collections are not swollen and short-septate; this feature only develops with maturity.


Further Online Information:

Boletus pseudosensibilis in Smith & Thiers, 1971
Boletus pseudosensibilis at Roger's Mushrooms

 

Boletus pseudosensibilis

Boletus pseudosensibilis

Boletus pseudosensibilis

Boletus pseudosensibilis

Boletus pseudosensibilis

Boletus pseudosensibilis

Boletus pseudosensibilis
Ammonia, KOH, iron salts

Boletus pseudosensibilis
Ammonia (video)

Boletus pseudosensibilis
Spore print

Boletus pseudosensibilis
Spores

Boletus pseudosensibilis
Pileipellis (young cap)

Boletus pseudosensibilis
Pileipellis (mature cap)

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Cite this page as:

Kuo, M. (2015, January). Boletus pseudosensibilis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_pseudosensibilis.html