Macroscopic features

  Pileus up to 9 x 8 mm when still closed, up to 18(-27) mm when expanded, first ellipsoid, cylindric-ellipsoid, ovoid or (sub)globose, expanding to campanulate or conical, than to convex or applanate, finally plano-concave with revolute margin, very thin, soon wilting, white in very young stage, soon becoming grey or grey-brown, the darkest (Mu. 5 YR 2.5/1, 3/2; 10 YR 3/2) at centre of pileus. Veil in primordia smooth, mat, pure white, later grey to grey-brown, covering entire pileus, soon radially splitting into hairy to fibrillose, often pointed and adpressed or - especially at centre - recurved flocks. Lamellae free, narrow, rather crowded, first white, soon grey to blackish; L = 34-40, l = 0-3. Stipe 15-45 x 1-2 mm, whitish, somewhat tapering towards apex, up to 3 mm wide at clavate to slightly bulbous base, hollow, hairy flocculose over the whole surface but particularly densely at lower part, becoming glabrous with age.

Microscopic features

  Spores [240/12/8] 5.6-8.8(-10.6) x 4.3-5.8(-7.1) µm, ellipsoid to ovoid tending to mitriform or rhomboid, with rounded or slightly conical base and rounded apex, and central, 1-1.5 µm wide germ pore; Q= 1.15-1.70, av. Q= 1.35-1.45; av. L = 6.6-9.2, av. B = 4.8-6.5 µm, dark red-brown. Basidia 18-32 x 7-11 µm, 4-spored, surrounded by (3-)4-5(-6) pseudoparaphyses. Pleurocystidia 70-125 x 22-33 µm, ellipsoid to ovoid, oblong or narrowly fusiform, the latter 7-13 µm wide below apex. Cheilocystidia in very young pileus broadly utriform, then rather elongate and ellipsoid, clavate, narrowly (conico-)utriform or oblong, 25-105 x 12-40 µm, the narrowly utriform ones 7-12 µm in diam. below apex. Pileipellis consisting of short, inflated cells, covered with a thin layer of filamentous hyphae. Veil made up of hyphae consisting of sausage-like cells, 20-150 x 5-40 µm, often somewhat inflated, usually constricted at septa. Clamp-connections present.

Habitat & distribution

  Solitary or (sub)fasciculate on soil mixed with pieces of wood, on decaying wood-chips and on composted vegetable refuse. Rather common. Only known from the Netherlands.

Remarks

  Coprinus geesterani is characterized by small fruit-bodies and ellipsoid to ovoid spores tending to mitriform or rhomboid shapes, on the average less than 9 µm long and on the average qoutient up to c. 1.45.
  The closest species Coprinus pseudoradiatus (1944: 26) often grows on dung, less frequent on naked soil (probably mixed with dung) and has spores more ellipsoid or oblong with a rounded, never somewhat conical base and a quotient more than 1.45. Coprinus lagopides has spores similar in shape and size to those of C. geesterani (although usually slightly broader), but that species has much larger fruit-bodies and grows generally on burnt ground.