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Species Information
Summary: Gymnopilus penetrans is a member of Arora''s Gymnopilus sapineus group but (like G. flavidellus) with a smooth yellow to yellow-orange cap and a whitish evanescent veil, (Arora). Distinctive characters include a bald cap, white flesh, gills that are rusty-spotted at maturity or when old, a white veil, no pileocystidia, and caulocystidia that are gregarious or in tufts, (Hesler).
Hesler studied material from WA, OR, ID, QC, CA, ME, MI, MO, TN, TX, WY, Jamaica, and Sweden. It was reported from BC by Schalkwijk-Barendsen and by Paul Kroeger (voucher at University of British Columbia). Collections from France, Netherlands, and Switzerland were used by Guzman-Davalos(2).
Cap: 3-5cm across, bell-shaped - convex then subplane [more or less flat]; chrome yellow to golden and fading flavescent [yellowish]; bald, not viscid, (Hesler), 2-5cm across, "bell-shaped to convex then flattened, often with a wavy margin; chrome yellow to golden then tawny" and fading yellowish when old; smooth, (Phillips), "brownish orange-yellow to reddish yellow or pale red-brown, usually with a lighter edge when expanded"; smooth to slightly scaly, (Trudell)
Flesh: white or whitish (Hesler), whitish, (Phillips)
Gills: adnate to sinuate, close, medium broad; "at first pale yellow or yellowish white", becoming rusty-spotted when old, (Hesler), "adnate, close, moderately broad; gold or yellowish white becoming tawny-spotted", (Phillips), yellowish, often red-spotted when old, (Trudell)
Stem: 4-6cm x 0.4-0.7cm, equal or sometimes widening downward; pallid, paler than cap, base white-tomentose, (Hesler), 4-6cm x 0.4-0.7cm, sometimes enlarged toward base; yellowish, base whitish with downy hairs, (Phillips), yellow to russet, (Courtecuisse), yellow top and bottom half red-brown to dark brown, (Schalkwijk-Barendsen), whitish to yellowish, typically becomes reddish brown in lower part; often with whitish veil fibrils on surface; white cords often extend from the stem base into substrate, (Trudell)
Veil: white, fibrillose, fugacious [fleeting], (Hesler), fibrous, white, leaves no ring, (Phillips), veil "whitish to pale yellowish and usually disappears as the fruitbody develops, although some specimens retain a slight fibrillose ring", (Trudell)
Odor: none or mild (Hesler, Phillips)
Taste: bitter (Hesler, Phillips), very bitter (Trudell)
Microscopic spores: spores (6.5)7-9(9.5) x 4-5.5 microns, elliptic in face view, somewhat almond-shaped in side view, verrucose, dextrinoid, no germ pore; basidia 4-spored, 24-31 x 6-7 microns; pleurocystidia 25-33(50) x 4-7 microns, ventricose, cheilocystidia 25-34(48) x 3-7 microns, "flask-shaped, apices capitate or non-capitate, at times expanding up the sides of the gills"; gill trama of subparallel hyphae 4-7 microns wide; cap trama radial, cap cuticle "of repent, sometimes incrusted hyphae", pileocystidia none; caulocystidia 30-50(66) x (2)6-8(13) microns, "flask-shaped to clavate, more or less capitate, gregarious or in tufts"; clamp connections present, (Hesler)
Spore deposit: orange-brown (Phillips)
Habitat / Range
on wood of conifers and hardwoods, at times on sawdust, summer and fall, (Hesler), "singly or in small tufts on hardwoods and conifers", July to October, (Phillips), common on conifer and hardwood stumps, logs, wood chips, and sawdust, (Trudell), summer, fall
Similar Species
Gymnopilus sapineus has a scaly cap, a yellow veil and pileocystidia, (Hesler), "Some mycologists have separated several very similar species from G. penetrans, including G. sapineus, with a scalier cap, and G. hybridus, with a fibrillose ring and spotted gills", (Trudell(4), with Latin names italicized). Gymnopilus flavidellus has a pallid veil, the odor is sometimes aromatic or radish-like, and pileocystidia are present, (Hesler) and the stem stains orange-brown when handled (Arora). See also SIMILAR section of Gymnopilus aurantiophyllus and Gymnopilus subsapineus.
