Summary:
Distinctive features are the dark red fibrils or scales on the cap (and often the stem), yellow gills, relatively persistent veil, and rusty-orange spores, according to Arora(1). Other features include dry cap surface that becomes yellowish when old, a dry stem that is colored more or less like the cap, becoming yellowish or rusty-stained when old, bitter taste, and fruiting in groups or clusters on wood. According to Hesler(2) the chief distinctive characters are 1) dark red to reddish brown young caps with the colors fading to pinkish red or yellowish red then yellow, 2) the reddish or vinaceous cap flesh that fades to yellowish, 3) the dextrinoid spores, and 4) the caulocystidia. Siegel(2) comment that Gymnopilus aeruginosus "may be a more appropriate name for the species profiled" [as Gymnopilus luteofolius] "but until this assertion is backed by more conclusive evidence, we have chosen to continue using the more familiar name".

Cap:
2-12cm across, convex or obtuse becoming nearly flat, margin inrolled at first; at first covered with dense dark red to purple-red or reddish brown fibrillose scales, these fading slowly to pinkish red or yellowish red, surface finally yellowish when old as scales disperse; dry, (Arora), 2-6(8)cm across, convex, obtuse; when young, dark red to reddish brown from dense fasciculate scales, "then fading to pinkish red or yellowish red, finally yellowish"; dry, margin fibrillose or appressed-scaly, even, (Hesler), convex, becoming broadly convex to nearly flat, margin "even, inrolled to incurved when young, soon straightening"; "dark red to reddish brown, fading in drying to pinkish red or yellowish red, and eventually yellow, sometimes bruising bluish green"; "dry, covered with dense, often fibrillose, and appressed purple-red to orangish scales", these disappearing when old, margin "adorned with fibrillose veil remnants", (Stamets)

Flesh:
thick, reddish to lavender, then fading to yellowish, (Arora), "at first reddish, light purplish vinaceous, or lavender, fading to yellowish", (Hesler), thick; "reddish to purplish, then fading to yellowish in drying", (Stamets)

Gills:
"notched to adnate or slightly decurrent, fairly close", yellow becoming bright rusty orange or rust-colored as spores mature, (Arora), "adnate or uncinate to emarginate", "close or subdistant, broad or medium broad"; at first yellow ("antimony yellow" to "honey yellow" - Ridgway(1) colors), then bright ferruginous; edges serrate, (Hesler), "adnate to sinuate, to slightly decurrent, close to subdistant, broad"; yellow becoming rusty orange; edges serrated, (Stamets)

Stem:
3-10cm x 0.3-2cm, equal or widened in lower part, or narrowing downward if clustered, solid, fleshy; "more or less colored like cap, becoming yellowish or rusty-stained"; dry, fibrillose, (Arora), 3-9cm x 0.3-1cm, equal or widening downward, solid; colored as cap; fibrillose, (Hesler), 3-8cm x 0.3-1cm, equal to widening downwards when forming singly, and narrowing when forming clusters, often curved at base; yellowish or stained rust-colored when old, base of stem sometimes bruising bluish, (Stamets)

Veil:
"fibrillose to somewhat membranous, yellowish", forming a hairy, superior ring on stem that may disappear, (Arora), arachnoid [cobwebby] to submembranous, yellowish, forming a fugacious [fleeting] ring, (Hesler), densely cortinate to nearly membranous, forming a superior membranous ring or fibrillose ring zone soon dusted with rusty orange spores, (Stamets)

Odor:
mild to pungent (somewhat alkaline), (Hesler)

Taste:
bitter (Arora, Hesler)

Microscopic spores:
spores 5.5-8.5 x 3.5-4.5 microns, elliptic, roughened, (Arora), spores (5.5)6-8.5 x (3.5)4-4.5 microns, elliptic to suboval in face view, slightly inequilateral in side view, verruculose [finely warty], "ferruginous in KOH, dextrinoid, no germ pore"; basidia 4-spored, 24-28 x 6-7 microns; basidioles 21-30 x 5-8 microns, brown, clavate, or more often ventricose and the apices acute; pleurocystidia 30-38 x 5-10 microns, "colorless, fusoid to ventricose", cheilocystidia 23-28 x 4-7 microns, "ventricose to flask-shaped, capitate to non-capitate"; caulocystidia 20-63 x 3-10(15) microns, "clavate, ventricose, or flask-shaped, forming a turf"; clamp connections present, (Hesler), spores 5.5-8.5 x 3.5-4.5 microns, elliptic, roughened; basidia 4-spored; pleurocystidia 30-38 x 5-10 microns, fusoid to ventricose, cheilocystidia 23-28 x 4-7 microns, ventricose to flask-shaped with or without a swollen head, (Stamets)

Spore deposit:
bright rusty orange (Arora), rusty orange (Stamets)

Notes:
Material was examined from WA, OR, ID, FL, MI, NC, NM, NY, OH, TN, and TX, (Hesler). It has also been found in CA (Desjardin) and BC (Stamets).

EDIBILITY

unknown (Arora), said to be hallucinogenic according to anecdotal reports, (Stamets)

Synonyms and Alternate Names:
Pholiota luteofolia (Peck) Singer