Universal veil

In mycology, a universal veil is a temporary membranous tissue that fully envelops immature fruiting bodies of certain gilled mushrooms.

[1] The developing Caesar's mushroom (Amanita caesarea), for example, which may resemble a small white sphere at this point, is protected by this structure.

The veil will eventually rupture and disintegrate by the force of the expanding and maturing mushroom,[2] but will usually leave evidence of its former shape with remnants.

These remnants include the volva, or cup-like structure at the base of the stipe, and patches or "warts" on top of the cap.

A membrane enveloping immature fruiting bodies of gasteroid fungi resembles a universal veil, but is called a peridium.

Immature fruiting bodies of two different mushrooms encased in a universal veil - deadly poisonous Amanita phalloides (left) and edible Amanita caesarea (right)
The white patches on the caps of these Amanita muscaria mushrooms are remnants of universal veils.