On the type of Coprinus pachydermus
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Original description
Coprinus pachydermus Van De Bogart in Mycotaxon 8: 274. 1979 (The genus Coprinus in Western North America, part 2: sect. Lanatuli). Holotype: North America: state Washington, Univers. Washington, 5 Oct. 1971, F. Van De Bogart 237 (WTU).

Pileus glandiform at first, then conic, then campanulate, and finally revolute and somewhat laciniate. Prior to expansion 0.8-1.1 cm in length and after expansion 1.8-2.2 cm in breadth. Pale grey-white to medium brown at apex at first, then generally darkening as spores mature. Surface faintly striate, but very little plicate striation develops. Entire surface covered at first by a hyaline to pale brown fibrous-scaly universal veil, and when fresh small glistening drops are present. The universal veil is loosely attached and easily dislodged and lost. The true surface is smooth and glabrous. Flesh thin and membranous. Stipe hollow, slender and thin, tapered slightly from base to apex, 6.0-8.5 cm x 2.0-3.0 mm. White, slightly translucent. Surface slightly wooly to silky at apex, becoming increasingly wooly towards the base. Flesh thin and fragile. Lamellae narrowly lanceolate, some short lamellae present, 4.0-l0.0 x 2.0-3.0 mm, free and remote, crowded and remaining so until destroyed by lysis, pale then black. Autodigestion destroys the entire pileus. Odor and taste none.
Spores ellipsoidal, nearly round in cross-section, 10.0-11.5 x 6.0-6.4 µm, lacking a perisporium, apiculus large and conspicious, germ pore apical, 1.2-1.4 µm in diameter. Color en masse soot black, microscopically deep brown in 3% KOH. Spores mostly with one guttule. Walls smooth. Basidia dimorphic, short clavate and 16.5-19.0 x 7.0-8.0 µm, long clavate and 25.0-27.5 x 7.5 µm, all four-spored. Cheilocystidia probably present but destroyed by lysis of lamellar margin. Pleurocystidia scattered widely over entire lamellar face, not plentiful, not bridging the interlamellar spaces, subglobose and 45.0-50.0 µm in diameter or short ellipsoidal and 68.0 x 40.0-48.0 µm, apices rounded, hyaline, thin walled, smooth. No other cystidia present. Pileal surface of radially oriented hyphae. Universal veil present on pileus as small white upturned loose scales composed of bundles of chains of ellipsoidal to subcylindrical cells, the chains of cells often exceeding 1200 µm in length. Individual cells 50.0-210.0 x 10.0-45.0 µm in size, hyaline, mostly somewhat swollen and constricted at the septa, some of them thin walled but most with walls up to about 1.5 µm thick, smooth, usually with clamp-connections, unbranched. Clamp-connections present on the universal veil, in the pileal trama, and also (a few) on the stipe surface.
Habitat. Lignicolous or sublignicolous, on an open compost pile of rotting wood chips and sawdust. In loose groups.

The exceptionally thick walls of most of the cells of the universal veil and the short subglobose pleurocystidia are distinctive.

Observations:
Spores [20,1,1] 9.3-11.0 x 5.7-7.2 µm, ellipsoid or ovoid, with rounded base and apex (base in part tending to conical), and central to slightly eccentric, c. 1.3 µm wide germ pore, medium to dark red-brown; Q = 1.40-1.75, av. Q = 1.55; av. L = 10.1, av. B = 6.5 µm. Basidia 22-34 x 6-9 µm, 4-spored, surrounded by 3-5 pseudoparaphyses. Pleurocystidia 60-90 x 24-35 µm, utriform or subcylindric. Cheilocystidia 30-50 x 18-25 µm, (sub)globose, ellipsoid or subutriform. Pileipellis hyphoid, made up of mainly inflate hyphae; elements 20-100 x 10-30 µm. Veil made up of hyphoid, thin- or slightly thick-walled elements (0.2-0.7 µm thick), 40-180 x 12-40 µm, in part somewhat inflated and constricted at septa; terminal cells subfusiform. Clamp-connections present.

Notes: The type materialconsists of a single baidiocarp and a fragment in bad condition, but most microscopical features could be found.
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