E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Section Celluloderma. Pluteus aurantiorugosus is characterized by a bright red to orange-red cap with whitish to pinkish free gills, a whitish fibrillose to fibrillose-scaly stem, a pinkish spore deposit, and growth on wood.

Lincoff(2) gives the range as northeast North America west to the Rocky Mountains. It is reported from the Rockies at least in BC (M. Beug. pers. comm.). P. aurantiorugosus is not common. Homola(1) examined collections from MI, MN, and OH. Minnis(1) examined collections from CA, IL, MI, and MN. The distribution includes Europe and it has been reported from Asia.

Cap:
(1.5)2-5.2cm across, at first obtusely conic to convex, expanding to flat-umbonate or flat, margin lobed and becoming finely cracked, involute at first; somewhat hygrophanous, brilliant scarlet to bright vermilion to orange-vermilion, fading to orange ("cadmium orange") or yellow ("cadmium yellow"); bald or slightly velvety and fibrillose especially when dry, smooth to rugulose [finely wrinkled] except on margin, margin indistinctly striate, (Homola), 2.5-5.5cm across, convex to nearly flat with small central umbo; "bright red to orange, fading to bright yellow"; granular, (Lincoff), striate toward margin (Barron)

Flesh:
0.4cm at stem; whitish to yellowish, in stem yellowish, (Homola)

Gills:
"slightly adnexed to free and becoming remote, crowded to close", about 0.6cm broad; "whitish to pallid to pinkish"; edges fimbriate [fringed], (Homola), "free, close, broad; whitish becoming pinkish", (Lincoff)

Stem:
3-6cm x 0.3-0.8cm, equal or widening slightly downward or narrowing slightly downward, straight or curved, splitting in some specimens, round in cross-section; "whitish to yellowish at first then orange to red at base", the top lighter; "striate, fibrillose to fibrillose-scaly when young, at maturity only fibrillose toward base", white mycelium at base, (Homola), 3-6cm x 0.3-1cm, "whitish to yellowish, becoming reddish near base"; with thin fibrous lines, (Lincoff)

Veil:
[none]

Odor:
none (Miller)

Taste:
bitter (Miller)

Microscopic spores:
spores 6-7 x 4.5-5 microns, ovate in side view, in face view ovate, narrowing somewhat toward apex, round in end view, with slightly thickened wall, nearly colorless to very pale yellow in KOH; basidia 4-spored, 20-22 x 6 microns, "mostly elongate-clavate to somewhat fusoid-ventricose"; pleurocystidia very scattered to rather common near edges, 44-76 x 18-31 microns, "saccate to clavate to fusoid-ventricose with a somewhat elongated neck and obtuse apex, thin-walled", colorless, cheilocystidia forming nearly sterile gill edges, 25-64 x 9-28 microns, "mostly smaller than pleurocystidia, saccate, or clavate and with an apical nipple, or merely clavate to fusoid, or subfusoid-ventricose with a short neck and obtuse apex, thin-walled", colorless; clamp connections absent, at least from cap cuticle and trama, (Homola), spores 6-7 x 4.5-5 microns, elliptic, smooth, (Lincoff), spores ovate, often oblong; cap cuticle lacking cystidioid elements, (Minnis)

Spore deposit:
pinkish (Homola), salmon-pink (Lincoff), pinkish brown (Miller)