Veil (mycology) Clearly visible webby partial veil (cortina), hiding the stalk. A veil or velum, in mycology, is one of several structures in fungi, especially the thin membrane that covers the cap and stalk of an immature mushroom.[1] Veils fall into two categories: Partial veil Universal veilReferences ^ [1] Archived 2007-01-10 at the Wayback Machine Encarta Dictionary