AppearanceThe cap is initially 1–2.5 cm in diameter, oval to cylindrical, but expands to become campanulate, sometimes with an umbo; finally it flattens somewhat, becoming convex. When expanded, the cap diameter reaches.8–5 cm with the margin torn into rays and turned upwards slightly. The color is yellow-brown or tan often with a darker center, then pale yellow or buff from the margin inwards. The cap margin is prominently grooved almost all the way to the center; the grooves mark the positions of the longer gills on the underside of the cap. When young, the cap surface is covered with white or whitish shiny particles, remnants of the universal veil that covers immature specimens. The particles are loosely attached and easily washed away, so that older specimens are often smooth. "Coprinellus micaceus" is hygrophanous, meaning it assumes different colors depending on its state of hydration.
The gills are crowded together closely, and have an adnexed attachment to the stipe. Initially white, they change color to dark brown then eventually black as the spores mature. Expansion of the cap causes the gills to split open down their median planes, tearing the cap margin into rays. The process of spore discharge and autodigestion begin at the bottom of the gills before the upper parts of the gills have become completely blackened. The brittle stipe is hollow, and measures 3–10 cm long by 2–5 mm thick and is roughly the same diameter throughout the length of the stipe. It is generally white but may discolor to pale dirty cream from the base up. The stipe surface is at first velvety with a very fine whitish powder, but this eventually wears off, leaving it more or less smooth. Stipes may have a rudimentary ring at the base, another universal veil remnant....hieroglyph snipped... The spore print is dark brown or black. The flesh is thin, fragile, white in the stipe, and brownish in the cap. Its odor and taste are not distinctive. Individual fruit bodies take an average of five to seven days to fully mature.The spores of "C. micaceus" are reddish-brown or black, with dimensions of 7–10 by 4.5–6 µm. Generally, they are lentiform, but viewed from the side they appear more almond-shaped or spindle-shaped, while in front view they appear oval or mitriform. Spores have a germ pore, a flattened area in the center of the spore surface through which a germ tube may emerge. The spore-bearing cells are four-spored, club-shaped, and measure 10–15 by 4–7 µm. Studies have shown that the basidia develop in four discrete generations. The first generation basidia are the most protuberant and extend out the greatest distance from the surface of the hymenium. Subsequent generations of basidia have shorter and less protuberant bodies. When a living gill is viewed with a microscope, the four sets of basidia can be seen distinctly. Arthur Buller coined the term "inaequihymeniiferous" to describe this mode of hymenial development. The purpose of the staggered basidia sizes is to facilitate the release of spores from the hymenium. There are four zones of spore discharge that correspond to the four sets of basidia, and basidia that have released all of their spores quickly begin to autodigest. The staggered setup minimizes the chance of spores colliding with neighboring basidia during release.
Cystidia that are located along the edge of the cap are spherical, and 30–120 by 20–74 µm. The facial cystidia are club-shaped or elongated ellipses, up to 130–155 µm in length. The pleurocystidia protrude from the face of the gill and act as guards, preventing adjacent gills from touching each other, and also ensuring that the basidia and spores have sufficient room for development. "C. micaceus" may also have scattered caulocystidia that are 60–100 by 5–10 µm, but their presence is variable and cannot reliably be used for identification. Both De Bary and Buller, in their investigations into the structure of the cystidia, concluded that there is a central mass of cytoplasm formed where numerous thin plates of cytoplasm meet at the center of the cell. De Bary believed that the plates were filamentous branching processes, but Buller thought that they were formed in a process similar to the walls of foam bubbles and that the central mass was able to slowly change form and position by altering the relative volumes of the vacuoles enclosed by the numerous thin cytoplasmic walls. In older cells, the cytoplasm may be limited to the periphery of the cell, with one huge vacuole occupying the cell center.
The globular cells that make up the mica-resembling scales on the cap are colorless, smooth-walled, and range in size from about 25–65 µm, although most are between 40 and 50 µm. Buller explained the "glitter" of these cells as follows: "The sparkling of the meal-cells, as well as of the cystidia on the edges and faces of the gills, is simply due to light which strikes them from without and is refracted and reflected to the eye in the same manner as from the minute drops of water one so often sees at the tips of grass leaves on English lawns early in the morning after a dewy night."
Distribution"Coprinellus micaceus" has a cosmopolitan distribution, and has been collected in northern Africa, South Africa, Europe, North America, the Hawaiian islands, South America, India, Australia, New Zealand, and Japan.
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