Annulus (mycology)

An annulus is the ring like structure sometimes found on the stipe of a mushroom. 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. The latter type of annulus is referred to as a cortina. 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".

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An annulus can be any of various shapes, which can be important in identification of the mushroom:

• pendant - drooping or skirtlike
• flaring - spreading outward from the stipe
• sheathing - opening upwards around the stipe