Mycotaxon 83: 47. 2002.
Common Name: none
Synonym: Clitocybe atrobrunnea H.E. Bigelow; Omphalina obscurata D.A. Reid
Cap 0.8-2.0 cm broad, convex, convex-umbillicate, to infundibuliform; margin decurved to level in age; surface radially appressed-fibrillose, the fibrils dark-brown over a pale-grey background, hygrophanous, fading in age to lighter shades of grey, sometimes with a satiny sheen when dry; context thin, approximately 1 mm thick, pale grey, unchanging; odor and taste not distinctive.
Gills subdistant, decurrent, medium-grey, up to 2 mm broad, the edges blackish with age; lamellulae in two to three series.
Stipe 1.0-1.5 cm long, 1-3 mm thick, hollow, straight to bent, more or less equal; surface glabrous, pale-grey at apex, becoming greyish-brown towards the base, surrounded by grey tomentum; partial veil absent.
Spores 6.5-9.0 x 3.5-5.0 µm, elliptical-oblong in face-view, elliptical to tear-shaped in profile, smooth, thin-walled, hilar appendage not conspicuous, inamyloid; spore deposit not seen.
Solitary or in small groups on bare soil, occasionally in moss in montane regions; fruiting in the spring; occasional to common in its preferred habitat.
Unknown; too small to have culinary value.
This small, omphaloid mushroom, also known as Clitocybe atrobunnea, is easily overlooked, its drab color closely matching the soils on which it often fruits, a feature reflected in the species epithet. Arrhenia obscurata is recognized by a dark-brown, appressed-fibrillose, often infundibuliform cap, and strongly decurrent gills. In California it is most likely to be confused with the similarly colored Arrhenia epichysium. The latter, however, occurs only on decayed wood
Bas, C., Kyper, T.W., Noordeloos, M.E. & Vellinga, E.C. (1995). Flora Agaricina Neerlandica—Critical monographs on the families of agarics and boleti occuring in the Netherlands. Volume 3. Tricholomataceae. A. A. Balkema: Rotterdam, Netherlands. 183 p.
Bigelow, H.E. (1985). North American Species of Clitocybe. Part II. J. Cramer: Berlin, Germany. 241 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Redhead, S.A., Lutzoni, F., Moncalvo, J.-M. & Vilgalys, R. (2002). Phylogeny of Agarics: Partial Systematics Solutions for Core Omphalinoid Genera in the Agaricales (Euagarics). Mycotaxon 83: 19-57.
Reid, D.A. (1958). New or interesting records of British hymenomycetes. II. Transactions of the British Mycological Society 41(4): 419-445.