The fruiting body size of Coprinopsis lagopus can vary tremendously. This fungus gives rise to very small fruiting bodies (known as dwarf fruit-bodies), some of which are less than one-hundredth the size of the larger ones. In a series of experiments, Arthur Henry Reginald Buller grew spores on horse dung and noted a large range of size variation: the smallest specimen having a stem length of 1 mm and cap diameter of 0.75 mm, while the largest specimen had a stem length of 184 mm and cap diameter of 20 mm. Buller noted that the dwarf fruit-bodies are fully functional, producing and liberating spores in a manner identical with normal ones. The great variation in size has led some authors to erroneously name the dwarf fruit-bodies as new species. For example, George Edward Massee considered the dwarfs to be a new species, Coprinus radiatus. In general, dwarf fruit-bodies have stem lengths from 1–10 mm tall and cap of 0.75–3 mm in diameter, while large specimens have stems that are 130–185 mm tall and cap diameters of 25–40 mm. The thickness of the stem in the larger specimens is typically 4–6 mm thick, up to 0.8 mm thick at the club-shaped or bulbous base.
The color of the cap surface is pale to very dark-brown at center beneath the whitish to silvery grey veil, but becomes paler towards the margin. As the mushroom matures, the shape of the cap becomes more conical or convex, and finally flattens out, with edges curved upward. The veil is initially whitish, then turns to a silvery grey or grey-brown; it eventually splits up, becoming hairy (fibrillose). The gills are freely attached to the the stem, very thin and crowded closely together. Initially the color of the gills is white, then progresses to grayish brown then to black as the spores mature. In maturity the gill edges dissolve (deliquesce) into a black liquid. These mushrooms are evanescent, lasting only last a few hours before death; the autodigestive process is enhanced in humid environments. The stem is whitish in color, and is hollow, hairy (flocculose) over the whole surface but especially at lower part, and becomes smooth (glabrous) with age. The spore print is violet-black.
The content for this page is adapted from the Wikipedia article on Coprinopsis lagopus. See that article for detailed references, authorship and references