Pileus up to 29 x 12 mm when still closed, up to c. 30 mm when expanded, first ellipsoid, cylindric-ellipsoid, often somewhat conical, white in very young stage, soon becoming greyish or grey-brown, the darkest at centre of pileus, expanding to conical, then to convex or applanate, finally plano-concave with revolute margin. Surface of pileus beneath veil first dark brown (Mu. 10 YR 4/3), later somewhat paler (10 YR 5/4). Veil in primordia smooth, mat, pure white, later grey to grey-brown (10 YR 7/3), covering entire pileus, soon radially splitting into hairy to fibrillose, often pointed and appressed or - especially at centre - recurved flocks. Lamellae, L = 32-46, l = 1-3(-5), free, narrow, rather crowded, first white, soon greyish brown to blackish. Stipe 50-100 x 2-4 mm, whitish, somewhat tapering towards apex, up to 5 mm wide at clavate to slightly bulbous base, hollow, hairy flocculose but particularly dense at lower part, becoming glabrous with age; base clavate with short and narrow pseudorhiza.
  Spores [60,3,3] 7.3-9.8 x 4.6-5.8 x 4.1-4.8 µm (without ornamentation); Q = 1.35-1.75, av. Q = 1.60; av. L = 8.0-8.4, av. B = 5.0-5.4, av. W = c. 4.4 µm, amygdaliform, towards base often slightly conical and lemon-shaped at apex, covered with many short, but broad and rounded nodules, with conical base and truncate apex, red-brown, and central, c. 1.3 µm wide germ pore. Basidia 13-24 x 6-8 µm, 4-spored, surrounded by (3-)4-5(-6) pseudoparaphyses. Pleurocystidia 30-150(-145) x 20-40 µm, ellipsoid to oblong or slightly broadly lageniform. Cheilocystidia 30-70(-90) x 20-35 µm, ellipsoid to oblong, sometimes slightly broadly utriform. Pileipellis a cutis, made up of cylindrical or fusiform, more or less parallel, repent hyphae, up to 150 µm long and 4-25 µm wide. Veil made up of inflate, sausage-like elements, 30-150(-250) x (3-)5-25(-40) µm, often somewhat inflated, usually constricted at septa. Clamp-connections present.

Habitat & distribution

  Habitat & distribution -- Growing fasciculate on stem of Yucca (indoors). Only known from the type-locality.

Remarks

  The amygdaloid spores with rounded nodules make it very easy to recognize Coprinus calosporus. No other Coprinus has such spores. The fact that the species is found indoors, in a flowerpot, makes it probable that it is a species from warmer regions than the Netherlands.