A veil or velum, in mycology, is one of several structures in

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, especially the thin

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

that covers the cap and stalk of an immature

mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...

.
Encarta Dictionary Veils fall into two categories: *

Partial veil In mycology, a partial veil (also called an inner veil, to differentiate it from the "outer", or universal veil) is a temporary structure of tissue found on the fruiting bodies of some Basidiomycota, basidiomycete fungus, fungi, typically agarics. ...

* Universal veil

References

Fungal morphology and anatomy {{Agaricomycetes-stub