Summary:
Arora''s Gymnopilus sapineus group (which has yellow to orange-brown color, modest size, dry cap, growth on wood, and rusty-orange spores) includes G. bellulus, G. liquiritiae, G. penetrans, G. sapineus, G. flavidellus, and G. terrestris (which is Cortinarius renidens and will be excluded here). [G. picreus could be added.] G. sapineus is distinct by virtue of the small scales or fibrillose patches on the cap, (Arora). Other features of the group include close, yellow gills when young, more or less equal stem that is yellowish buff to yellow and becomes brownish when old or when handled, and often bitter taste. Hesler(2) gives the distinctive characters of Gymnopilus sapineus itself as yellow to tawny, floccose-squamulose cap, which fades and becomes cracked, color change of stem from yellow brown to brown where handled, yellow veil, rosettes of caulocystidia, and mounds of pileocystidia.

Cap:
(1)2-5(9)cm across, convex to nearly flat or sometimes obscurely umbonate; golden yellow to tawny-orange, the margin sometimes paler; "dry, usually with minute scales or scattered patches of fibrils", often cracking when old, (Arora), (1)3-5(9)cm across, hemispheric then flat-convex; "golden yellow to tawny, paler on margin", finally fading; minutely floccose-squamulose, at length rimose [cracked], (Hesler), up to 3.5cm across, convex at first, then flattening; rusty brown with yellow orange margin, (Schalkwijk-Barendsen)

Flesh:
firm; yellowish, (Arora), thick on disc, soft; yellow (Hesler), yellowish, (Schalkwijk-Barendsen)

Gills:
"attached (usually adnate), close"; yellow becoming rusty yellow to rusty cinnamon when old, (Arora), adnate, close, broad; chrome yellow, then fulvous-cinnamon or rusty yellow; edges minutely fimbriate [fringed], (Hesler), adnexed; golden yellow, then yellow-brown, mottled; serrate, (Schalkwijk-Barendsen)

Stem:
2.5-7cm x 0.3-0.7(1)cm, equal or narrowing slightly in lower part; yellowish buff to yellow, becoming brownish yellow when old or when handled, (Arora), 3-7cm x 0.4-0.7(1.2)cm, equal or subattenuated [narrowing slightly] downward, solid or stuffed then hollow; yellowish, brownish in lower part when handled; innately fibrillose, (Hesler), up to 3cm tall and 0.4cm wide, yellow top, the rest brown; tiny scales, (Schalkwijk-Barendsen)

Veil:
"yellowish, fibrillose, disappearing or leaving a few hairs" near top of stem which turn rusty from spores (Arora), yellowish, scanty, sometimes remnants on cap margin, fugacious [fleeting], (Hesler)

Odor:
strong (Hesler), not distinctive (Miller)

Taste:
usually bitter (Arora), often bitter (Hesler)

Microscopic spores:
spores 7-9(10) x 4-5.5 microns, elliptic in face view, inequilateral in side view, verruculose [minutely warty], no germ pore, dextrinoid (reaction sometimes takes up to 4 hours), ferruginous in KOH; basidia 4-spored, 24-28 x 5-7 microns; pleurocystidia inconspicuous, scattered, 23-32 x 5-7 microns, ventricose, cheilocystidia 22-40 x 5-7 microns, "ventricose, capitate or subcapitate, more rarely non-capitate"; gill trama subparallel, hyphae 4-10 microns wide, subhymenium not distinctive; cap trama radial, cap cuticle "a zone of repent, brown, often incrusted hyphae, bearing fibrils which may be in fascicles (scales), and with scattered mounds of brown, ventricose to clavate pileocystidia" measuring 24-30 x 5-8 microns, in discussion of G. flavidellus the cap cuticle of G. sapineus described as "composed of several layers of brown, incrusted, repent hyphae"; caulocystidia 37-57 x 3-7 microns, "with a slender neck, capitate, often in rosettes"; yellow pigment, soluble in KOH, present in gill trama, (Hesler), spores 7-10 x 4-5.5 microns, elliptic, minutely roughened, (Arora)

Spore deposit:
amber-orange to rusty orange to bright rusty brown, (Arora), "hazel" or "amber brown" (Ridgway(1) colors), (Hesler), rusty orange (Schalkwijk-Barendsen)

Notes:
Material was examined from WA, OR, ID, QC, CA, CO, FL, MA, ME, MI, MO, NH, TN, TX, VT, WY, and United Kingdom, (Hesler). There are collections from BC by Paul Kroeger at the University of British Columbia. A collection from Finland was used by Guzman-Davalos(2).

EDIBILITY

unknown (Arora)

Synonyms and Alternate Names:
Fulvidula sapinea (Fr.) Romagn.