Synonym: Collybia subpruinosa (Murrill) Dennis, Marasmius subpruinosus Murrill
Cap 1.5-4.0 cm broad, convex, expanding to nearly plane, sometimes with a low umbo; margin at first decurved, plane to slightly upturned in age; surface striate-rugulose, innately fibrillose, and when viewed with a hand lens, minutely pruinose; disc color in young material, chestnut-brown to dingy reddish-brown, elsewhere medium brown, occasionally tinged purplish-brown, hygrophanous, soon light-brown overall except for ribbed areas; flesh thin, less than 1 mm, up to 2 mm thick at the disc, cream-buff, unchanging or sometimes reddish where cut or bruised; odor and taste not distinctive.
Gills adnate to adnexed, subdistant, relatively narrow, dingy-buff, edges pruinose (use hand lens); lamellulae up to three-seried.
Stipe 2.0-5.0 cm long, 1.0-3.0 mm thick, straight, pliant, hollow to stuffed at maturity, equal to enlarged at the apex; surface longitudinally striate, cream-buff at the apex, dark-brown at base, overlain with a buff-colored pubescence; partial veil absent.
Spores 7.5-9 x 3.5-4 µm, ellipsoid to tear-shaped, smooth, thin-walled, inamyloid; spore print white.
Scattered to clustered on humus-rich soils, woody debris and logs; fruiting in late summer in watered areas and after the fall rains.
This small drab mushroom is recognized by a brown soon fading to tan cap which is striate-rugulose from margin to disc, an inconspicuously pubescent, slender stipe, and gills with pruinose edges. A related species, Gymnopus villosipes, abundant on conifer duff, is distingushed by a cap that is striate-rugulose only halfway to the disc, a more densely pubescent stipe, and gill edges which are lighter than the faces. Additionally, Gymnopus villosipes though similar in size has a thicker stipe relative to the cap, and a disc that tends to be depressed or umbillicate rather than slightly umbonate as in G. subpruinosus.