The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like. An annulus may be persistent and be a noticeable feature of a mature mushroom, or it may disappear soon after the emergence of the mushroom, perhaps leaving a few remnants on the stipe as an "annular zone".