Annulus (mycology)

The annulus represents the remnants of the partial veil, after it has ruptured to expose the gills or other spore-producing surface.

Ring shapes and structures can also vary between specimens of the same species and change with the age of the mushroom so multiple descriptions are sometimes used.

Even in species with distinctly identifiable rings they may not always be present or perfectly match descriptions so it can be beneficial to have multiple specimens to compare at different states of maturity.

Such rings have a variety of synonymous terms associated with them such as fleeting,[5] ephemeral,[4] evanescent,[6] transient,[7] fugacious[8] or impermanent.

However for species which otherwise look quite similar but exhibit differences in colouration, texture or staining above or below the stem ring, the position can be a useful factor to note.