Summary:
Leucopaxillus gentianeus is recognized by a dull brown to reddish-brown cap, close, narrow, white gills, a white stem, absent veil, a bitter taste, and white mycelium permeating the humus around base and often adhering to stem when picked. Singer(19) gives a key to forms of Leucopaxillus amarus that includes the following examined from the Pacific Northwest: 1) forma typicus with a dark cap (associated with abundant incrusting pigment on hyphae), 2) forma roseibrunneus, with a dull colored cap (incrusting pigment rather scarce and color produced by dissolved intracellular pigment), and 3) forma bicolor having a cap avellaneous with a rosy tint, but hyphae of cap cuticle colorless (no or very little incrusting pigment, very little intracellular pigment).

Cap:
5-12(15)cm across, broadly convex with inrolled margin when young, becoming flat or slightly depressed; dark brown to brown, pecan-brown, or reddish brown, evenly colored or paler at margin; "dry, unpolished, smooth", sometimes cracked or faded when old, margin often obscurely ribbed, (Arora), 4-12(15)cm across, "convex or very rarely obtusely umbonate, eventually more or less flattened or the disc depressed", the margin involute at first, spreading or wavy when old; deep reddish brown when young, becoming paler reddish brown when mature or when old; dry and subtomentose at first, sometimes becoming more or less bald, "sometimes more or less subsquamulose, in age at times verruculose-areolate to subrimose", margin sulcate at first, grooved when old, (Singer for f. typicus), dark to pale reddish brown on disc, buff to alutaceous along margin, (Singer for f. roseibrunneus), brownish pink with browner circular spots, margin paler with a cremeous tint, (Murrill for f. roseibrunneus), avellaneous with a rosy tint (Murrill for f. bicolor)

Flesh:
thick, firm, dry; white, (Arora), rather thick and firm; white, (Singer for f. typicus)

Gills:
"typically adnate but ranging from notched to slightly decurrent by lines", close, narrow; white, (Arora), "adnate and more or less sinuate" but frequently with prolonged ribs extending down top of stem, close (85-110), narrow (0.3-0.8cm broad), separable from cap flesh; "white, finally cream-white and then at times with ferruginous spots", (Singer for f. typicus)

Stem:
4-10cm x 0.5-2(4)cm, equal or enlarged in lower part, solid; white or sometimes discolored brownish in lower part; smooth, dry, base embedded in a copious white mycelial mat, (Arora), 4-6cm x 0.8-4.5cm, equal to bulbous, solid or becoming hollow; pure white or the base becoming sordid brownish when old where touched; top faintly pruinose, sometimes minutely pubescent overall, (Singer for f. typicus)

Veil:
none (Arora)

Odor:
mild or pungent (Arora), peculiar, either strong or very faint and like that of Tricholoma sulphureum but more farinaceous, (Singer for f. typicus), faintly farinaceous to strongly rancid farinaceous (Singer for f. roseibrunneus), farinaceous (Murrill for f. roseibrunneus), not noted for f. bicolor

Taste:
very bitter (Arora), bitter in f. typicus, "bitterish to somewhat farinaceous, strong at times" in f. roseibrunneus, (Singer), "farinaceous with a faint bitter flavor which gradually becomes stronger", (Murrill), not noted for f. bicolor

Microscopic spores:
spores 4-6 x 3-5 microns, nearly round, warted, amyloid; cheilocystidia numerous, (Arora), spores 4.3-6 x 3.7-5 microns, nearly round, with distinct, isolated strongly amyloid warts, thin-walled, with one oil droplet; basidia 4-spored, 27-33 x 6-7.5 microns, "sometimes with a few two-spored individuals intermixed"; pleurocystidia none, cheilocystidia "very abundant, with only scattered basidia among them", 25-38 x 2-6.5 microns, "variable in shape, fusoid, clavate-cylindric or bottle-shaped, never thickened at the base, sometimes forked or variously branched"; cap cuticle with hyphae "reddish brown inside from a dissolved pigment and, in addition, the walls covered by an abundant rufous-brown pigment incrusting the walls in the form of warts or rings or irregular plates", the hyphae thin-walled or part of them having moderately thickened walls; clamp connections noted for cap trama, (Singer for f. typicus); cap cuticle hyphae distinctly colored by a reddish brown dissolved intracellular pigment, with rather distinct but rare incrustations of a reddish brown to dark brown (in some places colorless) intercellular pigment "that forms but faint low markings on the thin or rather thin walls", (Singer for f. roseibrunneus)

Spore deposit:
white (Arora, Singer for f. typicus)

Notes:
Forma typica was examined from WA, ID, CA, WY, Europe, Caucasus, and North Africa, forma roseibrunneus was found in WA, OR, CA, ID, WY, and possibly Europe and Africa, and f. bicolor was found in WA, CA, and CO. There are collections of Leucopaxillus gentianeus from BC at University of British Columbia.

EDIBILITY

no (Arora)

Synonyms and Alternate Names:
Leucopaxillus amarus (Alb. & Schwein. ex Fr.) Kuehner (misapplied)