Universal veil

The universal veil is a mycological term to describe a structure that envelops all or most of some gilled mushrooms. The young, developing button mushroom, which may resemble a puffball at this point, is protected by this egg-like structure. The veil will eventually become ruptured and dispersed by the growing mushroom, but will usually leave evidence of its former shape with remnants including the volva, or cup-like structure at the bottom of the stalk stipe and patches or "warts" on the cap pileus. This macrofeature is very important in wild mushroom identification due to it being an easily observed, taxonomically significant feature which almost always signifies a member of Amanitaceae. This has particular importance due to the disproportionately high number of deadly poisonous species contained within that family.

Velum universale