Summary:
Features of Coprinellus ephemerus include small size, tall, thin, cinnamon brown cap, white stem, and pileocystidia microscopically on the cap. C. ephemerus was in Section Setulosi (with pileocystidia best seen just before opening) of Coprinus sensu lato along with Coprinellus congregatus, Coprinellus disseminatus, Coprinellus hiascens, and Coprinellus impatiens according to Moser. There are probably others in this section which has not been fully studied in the Pacific Northwest. Coprinellus ephemerus is the more recently published name based on molecular evidence (Redhead(49)).

Cap:
0.5-1.5(2)cm across, 0.5-1.5cm high, ovoid to cylindric, becoming conic to bell-shaped, expanded with uplifted margin when old, margin undulating [wavy] to split; "ocher-yellow when young, later increasingly gray from margin inward, center usually somewhat fox-brown"; "striate almost to the center at all stages, without a veil", deliquescing rapidly, (Breitenbach), 1-2cm, tall, thin; disc light to dark cinnamon brown, (Moser), 1-2cm high, bright brown; striate, (Hansen)

Flesh:
membranous; whitish, (Breitenbach)

Gills:
free, 20-25 reaching stem, 0-1 subgills between neighboring gills, broad; "whitish when young, quickly turning gray to black"; edges smooth, (Breitenbach), deliquescing (Moser)

Stem:
4-7cm x 0.1-0.2cm, cylindric, at times somewhat widened toward base, fragile; "hyaline-whitish to gray-brownish"; "entire length covered with fine white powder when young", bald when old, (Breitenbach), up to 7cm long and up to 0.3cm wide, white, (Moser), 3-7cm x 0.1-0.3cm, whitish, (Hansen)

Odor:
none (Breitenbach)

Taste:
mild, insipid, (Breitenbach)

Microscopic spores:
spores 11.3-15.8 x 6.4-8.6 microns, elliptic to amygdaliform [almond-shaped], smooth, dark tobacco-brown, with eccentric germ pore; basidia (2-)4-spored, 21-30 x 8-10 microns, clavate, without basal clamp connection; pleurocystidia not seen, cheilocystidia 25-50 x 8-35 microns, vesicular to fusiform-ventricose; cap cuticle of spherical cells 10-35 microns in diameter, with interspersed subulate pileocystidia 60-130 x 14-22 microns, no clamp connections seen, (Breitenbach), spores 8.6-16.7 x 5.3-8.5 microns, germ pore slightly eccentric; pleurocystidia 60-120 x 22-45 microns, cheilocystidia short, 20-60 x 20-30 microns; pileocystidia 33-94 / 9-19 / 3.5-8 microns, swollen at apex, (Moser); basidia 4-spored; pleurocystidia 60-120 x 22-45 microns, cheilocystidia short, 20-60 x 20-30 microns; pileocystidia 33-94 x 9-19 x 3.5-8 microns, swollen at apex; caulocystidia on stem, (Moser), spores 9-16 x 5.5-8.5 microns, pleurocystidia present; pileocystidia 40-90 microns long, not or slightly enlarged above; clamps present, especially on mycelium, (Hansen)

Spore deposit:
black (Breitenbach)

Notes:
Coprinellus ephemerus was reported from BC by Cheeseman 1910 according to Redhead(5). Breitenbach(4) give the distribution as North America, Europe, Asia, and North Africa.

EDIBILITY

Synonyms and Alternate Names:
Coprinus ephemerus (Bull. ex Fr.) Fr.