Summary:
Features include 1) small size, 2) a cap that is reddish-brown to fulvous to pale ochreous or buff striate and is often somewhat depressed centrally, 3) adnate subdistant yellowish brown to whitish gills, 4) a dark brown stem with an ochreous velvety coating, lack of odor, and growth on Dryas (mountain avens). Redhead(63) gives the microscopic distinguishing features as "large amygdaliform spores, mostly smooth pileipellis elements with sclerocystidia and the presence of elongated pleuro- and cheilocystidia". Ohenoja has suggested that M. epidryas occurs on Dryas remains because of the richness of the substrate which is in part due to the presence of nitrogen-fixing nodules on its roots. The online Species Fungorum, accessed March 16, 2016, gives the current name as Rhizomarasmius epidryas, but MycoBank gave that name as a synonym.

Cap:
0.4-1cm across, convex; "dark reddish brown and obscurely striate marginally when moist, fading to buff or pale ochreous or fulvous in older specimens, rugose, sometimes shallowly corrugated-striate marginally", (Redhead(63)), 0.5-1.3cm across, hemispheric - bell-shaped when young, later flat and with more or less strongly incurved margin which is acute and often wavy, cap somewhat depressed in center; ocher-yellow, paler to cream toward margin, "center darker to brown, often dark-brown punctate"; "dull, radially undulating from the margin inward, also weakly tuberculate", (Breitenbach), 0.5-1.5cm across, yellowish brown, (Hansen), up to 1cm across, copper-yellow, often somewhat depressed, (Moser), up to 1.5cm across, convex, with navel, and margin that stays incurved; brown soon fading on top; striate margin, (Schalkwijk-Barendsen)

Flesh:
pliant, whitish, (Redhead(63)), thin; white; in stem whitish, (Breitenbach), thin, tough; off-white, (Schalkwijk-Barendsen)

Gills:
adnate, subdistant, occasionally forked, one tier of subgills; light yellowish brown or buff, at times whitish, (Redhead(63)), broadly adnate, 14-16 gills reaching stem, 1-3 subgills between each pair of gills, broad; pale cream to ocherish; edges smooth, (Breitenbach), broadly adnate; whitish, (Hansen), distant; white, (Moser), adnate, distant, intermediates; ivory to buff, (Schalkwijk-Barendsen)

Stem:
2.5-5.6cm x 0.03-0.2cm, often narrowing downwards and subinsititious, "at times slightly swollen basally with copious matted buff to ochreous fibrils"; dark brick to blackish brown with ochreous velvety coating, sometimes buff apically, (Redhead(63)), 1.5-3.5cm x 0.07-0.15cm, cylindric, somewhat wider at top, "elastic, tough, hollow"; "dark brown to brown-black", apex paler; dull, "entire length finely pilose-pubescent", (Breitenbach), 1-3cm x 0.1-0.2cm, brownish black; pubescent, (Hansen), 1-3cm x 0.15-0.2cm, tapering at base; brown-black, pruinose, (Moser), up to 4cm long and up to 2cm wide, dark brown, top lighter, (Schalkwijk-Barendsen)

Odor:
not distinctive (Redhead(63)), none (Schalkwijk-Barendsen, Breitenbach)

Taste:
not distinctive (Redhead(63), Breitenbach)

Microscopic spores:
spores 8-11.2 x 5-6.5 microns, almond-shaped to elliptic, smooth, inamyloid, colorless, thin-walled, usually with a prominent large droplet, with a large prominent apiculus; basidia 4-spored, 35-50 x 7.5-9.8 microns, narrowly clavate, with clamp connection; pleurocystidia and cheilocystidia 45-50 x 4.2-8.0 microns, "similar although cheilocystidia shorter on average, scattered, prominently projecting, narrowly rostrate-clavate to narrowly fusoid, sometimes with a compressed capitate apex, thin-walled", colorless, smooth; gill trama and cap trama: hyphae 3.5-6 microns wide (scarcely inflated), interwoven, colorless, thin-walled, smooth, with clamp connections; pileipellis "a somewhat hymeniform layer of polymorphic clamped cells in one to two levels" obscurely embedded or agglutinated by a subgelatinous, colorless to brownish material, mainly of thin-walled to thick-walled nearly colorless to pale brownish sphaerocysts 9-17 microns in diameter, "with single or forked pedicels, occasionally papillate apically and sometimes developing a coralloid appendage", "mixed with less inflated ovate to pyriform or clavate cells and with embedded, reddish brown, clavate to cylindrical, often secondarily septate sclerocystidia" 29-49 x 5-9 microns; caulopellis: hyphae 3-4 microns wide, "parallel, reddish brown", "smooth to unevenly thickened", bearing numerous caulocystidia that are 30-120 x 4-8 microns, "abundant, scattered to clustered", cylindric, "sometimes contorted, thick-walled, brownish", stem trama: hyphae 3-8 microns wide, parallel, thin-walled, colorless, smooth, with clamp connections, "narrower and interwoven centrally", (Redhead(63)), spores 7.3-9.1 x 4.3-6.7 microns, citriform [lemon-shaped], elliptic, smooth, iodine negative, colorless, with droplets; basidia 4-spored, 35-40 x 8-10 microns, clavate, with basal clamp connection; pleurocystidia 38-45 x 9-11 microns, ventricose-capitate, slightly thick-walled, cheilocystidia 40-55 x 4.5-6.5 microns, fusiform-subulate, some with small knob at apex, slightly thick-walled; pileipellis a hymenoderm of cells 10-22 x 5-11 microns, vesicular to clavate, "some thick-walled, with light brown pigmentation, with a thin layer of a gelatinous substance over them", septa with clamp connections; hairs on stem apex colorless, thick-walled, brown-pigmented at the base, (Breitenbach), spores 8.5-10.5 x 5-7 microns, almond-shaped; cheilocystidia 50-70 x 5-9 microns, (Hansen); spores 8.5-10.5 x 5-6 microns (Moser)

Spore deposit:
white (Schalkwijk-Barendsen)

Notes:
Marasmius epidryas has been found at least in BC, AB, MB, NT, NU, YT, and AK, (Redhead(6)). It has also been found in Greenland and Europe.

EDIBILITY

Synonyms and Alternate Names:
Rhizomarasmius epidryas (Kuehner ex A. Ronikier) A. Ronikier