Suillus brevipes
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Ecology: Mycorrhizal with hard pines (species of Pinus with needles in bundles of two or three)— including lodgepole pine, red pine, and jack pine; growing alone, scattered, or gregariously; late summer and fall; originally described from "New England" (Frost 1874), and later from the Albany, New York area (Peck 1885); widely distributed in North America from the northeast to the Midwest, the Rocky Mountains, the southwestern United States, and the West Coast (but probably absent in the southeastern United States; see discussion above); reported from Mexico and from Oceania. The illustrated and described collections are from Colorado, Illinois, and Indiana.
Cap: 4-10 cm; convex becoming broadly convex or nearly flat; very slimy when fresh; bald; dark brown to dark reddish or orangish brown, fading to pinkish brown or yellowish brown, often in streaks; the margin at first incurved and pale, with a tiny sterile edge, but without veil remnants.
Pore Surface: Pale yellow, becoming dingy brownish yellow and eventually dark reddish brown; not bruising; 1-2 circular to angular pores per mm; tubes to about 5 mm deep; surface not boletinoid.
Stem: 3-7 cm long; 1.5-3 cm thick; swollen and squat when young, straightening out with maturity; often short, even at maturity; white at first, becoming pale to dark yellow, usually from the apex downward; sometimes bruising brownish; glandular dots usually tiny and concolorous with stem surface (nearly invisible without a hand lens); without a ring; basal mycelium white, or bright to dull yellow.
Flesh: White at first, especially in the cap; becoming yellow with age; not staining when sliced.
Odor and Taste: Not distinctive.
Chemical Reactions: Ammonia negative to pinkish on cap surface; pink on flesh. KOH dark gray on cap surface; purplish gray or blue, with a pink ring, on flesh. Iron salts negative or gray on cap; purplish to blue on flesh.
Spore Print: Brown to dull cinnamon.
Microscopic Features: Spores 5-10 (-12) x 2-3.5 m; boletoid-fusiform; smooth; yellowish in KOH. Basidia 20-25 x 4-6 m; clavate; 4-sterigmate. Cystidia in bundles; 30-70 x 4-10 m; cylindric-flexuous, with subclavate, subcapitate, or merely rounded apices; smooth; thin-walled; purple-brown to brown in KOH. Pileipellis an ixocutis; elements 3-7 m wide, encrusted with tiny pigment droplets, brownish in KOH.