 The cap is initially 1 – 2 @.@ 5 cm ( 0 @.@ 4 – 1 @.@ 0 in ) in diameter , oval to cylindrical , but expands to become campanulate ( bell @-@ shaped ) , sometimes with an umbo ( a central nipple @-@ like protrusion ) ; finally it flattens somewhat , becoming convex . When expanded , the cap diameter reaches 0 @.@ 8 – 3 @.@ 0 cm ( 0 @.@ 3 – 1 @.@ 2 in ) 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 . 
