Annulus (mycology)

An article about the annulus in mycology

Annulus (mycology)

A mushroom with a prominent annulus

In mycology, the annulus is a ring-like structure found on the stipe (stem) of certain mushrooms. It is a remnant of the partial veil, which is a membrane that covers the gills or other spore-producing surfaces of a young mushroom.

Formation

The annulus forms as the mushroom matures and the partial veil breaks, leaving a ring around the stipe. This structure can vary greatly in appearance, from a thin, fragile ring to a thick, robust band. The presence and characteristics of the annulus are important for the identification of many mushroom species.

Function

The primary function of the partial veil, and consequently the annulus, is to protect the developing spore-producing surfaces of the mushroom. Once the mushroom is mature and the spores are ready to be released, the partial veil breaks, and the annulus remains as a vestigial structure.

Variations

Annuli can be classified based on their texture, color, and persistence. Some annuli are delicate and may disappear as the mushroom ages, while others are more durable. The annulus can be smooth, striated, or even cobweb-like in appearance.

Importance in Identification

The presence or absence of an annulus, along with its characteristics, is a key feature used in the identification of mushrooms. For example, the Amanita genus is known for having a prominent annulus, while other genera may lack this feature entirely.

Related Structures

• Volva - A cup-like structure at the base of the stipe, also a remnant of a protective veil.
• Cap - The top part of the mushroom, which can also have remnants of the veil.
• Gills - The spore-producing structures that the partial veil initially covers.

Related pages

• Mushroom anatomy
• Fungal morphology
• Spore dispersal