 The gills are crowded together closely , and have an adnexed ( narrow ) attachment to the stem . 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 stem is hollow , and measures 4 – 10 cm ( 1 @.@ 6 – 3 @.@ 9 in ) long by 0 @.@ 2 – 0 @.@ 5 cm ( 0 @.@ 1 – 0 @.@ 2 in ) thick and is roughly the same diameter throughout the length of the stem . It is generally white , but may discolor to pale dirty cream from the base up . The stem surface is at first velvety with a very fine whitish powder , but this eventually wears off , leaving it more or less smooth . Stems may have a rudimentary ring at the base , another universal veil remnant . The spore print is dark brown or black . The flesh is thin , fragile , white in the stem , 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 . 
