 Coprinellus micaceus is a common species of fungus in the family Psathyrellaceae with a cosmopolitan distribution . The fruit bodies of the saprobe typically grow in clusters on or near rotting hardwood tree stumps or underground tree roots . Depending on their stage of development , the tawny @-@ brown mushroom caps may range in shape from oval to bell @-@ shaped to convex , and reach diameters up to 3 cm ( 1 @.@ 2 in ) . The caps , marked with fine radial grooves that extend nearly to the center , rest atop whitish stems up to 10 cm ( 3 @.@ 9 in ) long . In young specimens , the entire cap surface is coated with a fine layer of reflective mica @-@ like cells that provide the inspiration for both the mushroom 's species name and the common names mica cap , shiny cap , and glistening inky cap . Although small and with thin flesh , the mushrooms are usually bountiful , as they typically grow in dense clusters . A few hours after collection , the gills will begin to slowly dissolve into a black , inky , spore @-@ laden liquid — an enzymatic process called autodigestion or deliquescence . The fruit bodies are edible before the gills blacken and dissolve , and cooking will stop the autodigestion process . 
