North American Species of Crepidotus: 136. 1965.
Common Name: none
Cap 1.0-3.0 cm broad, at first cupulate, becoming kidney to shell-shaped; margin incurved, fringed with a cottony tomentum; surface covered with appressed white fibrils over an ochre-brown background, the attachment point sheathed in cottony-villose fibrils; context thin; odor and taste mild.
Gills close, radiating from the attachment point, cream-buff in youth, eventually tan-brown; lamellulae in 3-4 series, edges minutely fringed.
Spores 5.5-7.5 x 3.5-5.0 µm, broadly elliptical in face-view, similar in profile, slightly inequilateral, thin-walled, slightly roughened, hilar appendage not conspicuous; spores dull-brown in deposit.
Gregarious, often in rows on branches of downed montane conifers, also reported on hardwoods; fruiting in the spring shortly after snowmelt; common.
Principal fieldmarks of Crepidotus fimbriatus are small size, a pleurotoid shape, ochre-brown cap covered with whitish fibrils, and an incurved, fimbriate margin. Its snowbank habit, fruiting on the undersurface of downed conifer branches, is also a helpful though not infallible character. Many Crepidotus species are similar and a microscope is often needed to make an identification. Similar to Crepidotus fimbriatus and sometimes found fruiting with it is Lentinellus montanus. The latter can be distinguished by its generally larger size, pinkish-brown cap, serrated gills, bitter taste, and white spores.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Hesler, L.R. & Smith, A.H. (1965). North American Species of Crepidotus. Hafner Publishing Company: New York, NY. 168 p. (Protologue)