Summary:
Features of Stropharia melanosperma include 1) white, subviscid cap that may be pale grayish brown or yellowish in center, 2) narrowly adnate, ventricose, pale gray gills, 3) relatively tall and slender stem that is white to pale yellow, pruinose above the prominent, grooved annulus and striate in lower part, and 4) microscopic characters.

Cap:
3.0-7.0cm across, convex to flat-convex, "sometimes with umbo, with straight margin"; when moist white to pale grayish brown, often with slight yellow tint at center, "white when dry"; smooth, bald, "veil practically absent"^, (Noordeloos), 3.0-5.0cm across, hemispheric-convex becoming convex to flat-convex, "margin incurved for a long time, acute, smooth; "whitish to gray-beige, center yellowish"; smooth, dull, slightly slimy when moist", (Breitenbach), 7.2cm across, flat-convex to flattened, with slight umbo; white to yellowish white in center, "to white toward the margin"; "subviscid, with distinct but reduced and scattered yellowish scales from center to the margin", "margin regular to somewhat crenate, non-striate, with conspicuous appendiculate white velar remains", (Cortez), 3-6cm across, white; "dry to moist but not viscid, smooth", "margin often rimmed with torn partial veil remnants", (Bessette)

Flesh:
white to pale yellow^ (Noordeloos), thin; white, (Breitenbach), soft, fleshy, 0.7cm thick at disc; white, (Cortez)

Gills:
narrowly adnate, ventricose, moderately distant, 20-35 gills reaching center, 1-5 subgills between neighboring gills; pale gray then grayish black "with concolorous or paler, fimbriate edge", (Noordeloos), "ascending and narrowly adnate", broad, 30-36 reaching stem, 3-5 subgills between neighboring gills; "whitish when young, later gray-violet, violet-black when old"; edge white-floccose, (Breitenbach), "adnexed, close to crowded", not reaching cap margin; grayish violet when mature; "distinct pale edge", (Cortez)

Stem:
4-10cm x 0.5-1.3cm, cylindric or widening gradually toward base; "white to pale yellow"; "finely pruinose above annulus, striate in lower part", (Noordeloos), 3.5-7.0cm x 0.5-0.8cm, cylindric, "solid when young, hollow when old, rigid, fragile"; white; finely white-powdered above the annulus, finely longitudinally white-fibrillose below the annulus, slightly browning toward base, (Breitenbach), 12.4 x 1.6cm, central, fibrous in consistency, hollow, clavate to subcylindric, "with an expanded to sub-bulbous base"; yellowish white to pale yellow; moist, with reduced white scales at top and base, absent in the middle, "rhizomorphs and basal mycelium very abundant", (Cortez), 3-8cm x 0.4-0.8cm (Bessette)

Veil:
annulus [ring] "prominent, membranaceous, pendant, with distinctly grooved upper surface", (Noordeloos), annulus white, pendant, membranous, upper surface striate, becoming brown from spores, (Breitenbach), producing appendiculate white remains on cap margin, and a thick, fleshy annulus, "which is violaceous and grooved above and smooth and white below", (Cortez), ring superior (Bessette)

Odor:
"slightly unpleasant when cut or bruised", (Noordeloos), almost odorless (Breitenbach)

Taste:
mild (Noordeloos), mild, rather unpleasant, (Breitenbach)

Microscopic spores:
spores 10.0-12.5(13.0) x 6.5-8.5(9.0) microns, elliptic to oblong, "sometimes somewhat flattened in side view, sometimes subhexagonal or mitriform in frontal view, very thick-walled with prominent germ pore"; basidia 4-spored, 18-35 x 7.0-11 microns; pleurochrysocystidia rather numerous, 32-50 x 10-15 microns, lageniform with 2.7-7.0 microns wide neck; gill edge sterile, cheilochrysocystidia 35-45(50) x 15-25 microns, "lageniform or ventricose-rostrate" with 2.5-6.0 microns wide, acute neck, cheiloleptocystidia absent; acanthocytes not seen; clamp connections present, (Noordeloos), spores 9.2-11.5 x 6.2-7.4 microns, "elliptic-amygdaliform, smooth, olive-brown, thick-walled, with a germ pore"; basidia 4-spored, 22-32 x 8-10 microns, cylindric, without a basal clamp connection; cheilocystidia 28-48 x 9-17 microns, "fusiform to clavate, usually with an apical protrusion", "contents coloring faintly in cotton blue", "pleurocystidia similar but only fusiform"; some septa with clamp connections, (Breitenbach), spores (10.5)11-12.5(13.5) x 7.5(9.0) microns, elliptic in side view, to slightly ovoid in front view, smooth, yellowish brown, thick-walled, with truncate germ pore; basidia 4-spored, (26)28.5-33.5 x 9-12 microns, clavate, colorless; pleurocystidia as chrysocystidia (30)35-44(50.5) x 8.4-10(12) microns, "clavate to fusoid with a short-rostrate apex or clavate with a mucronate apex, thin-walled, colorless but with amorphous golden yellow contents", cheilocystidia as chrysocystidia very numerous, (26)31-40(44.5) x 10.5-12.6(15) microns, "fusoid to ventricose, with an acute, mucronate apex", thin-walled, colorless, "with amorphous golden yellow contents"; acanthocytes present abundantly on rhizomorphs; clamp connections present at most septa, (Cortez)

Spore deposit:
purplish black, (Noordeloos), dark brown (Breitenbach), dark violet (Cortez)

Notes:
It has been recorded and vouchered from BC by Paul Kroeger (pers. comm.), and there is a collection from WA at the University of Washington; occurs elsewhere in North America; distribution also including Brazil, Austria, Germany, Netherlands, Russia, Switzerland, and Argentina, (Cortez(1)); examined from NY, distribution includes New England, TX, Costa Rica, Europe, (Murrill(6))

EDIBILITY

edible (Bessette)

Synonyms and Alternate Names:
Psilocybe melanosperma (Bull.) Noordel.