Wiktionary
n. (context mycology English) A thin layer of tissue which completely surrounds a developing mushroom.
WordNet
n. membrane initially completely investing the young sporophore of various mushrooms that is ruptured by growth; represented in the mature mushroom by a volva around lower part of stem and scales on upper surface of the cap [syn: velum]
Wikipedia
In mycology, a universal veil is a temporary membranous tissue that fully envelops immature fruiting bodies of certain gilled mushrooms. 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, 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. This macrofeature is useful in wild mushroom identification because it is an easily observed, taxonomically significant feature. It is a character present among species of basidiomycete fungi belonging to the genera Amanita and Volvariella. This has particular importance due to the disproportionately high number of potentially lethal species contained within the former genus.
A membrane enveloping immature fruiting bodies of gasteroid fungi resembles a universal veil, but is called a peridium.
Usage examples of "universal veil".
The upper part of the universal veil remains on the surface of the cap, where by the gradual expansion of the same, it is broken up into irregular patches, which in most cases remain throughout the life of the fungus, hence one of the popular names Wart Caps.
After the universal veil has been ruptured and the cap has commenced to expand, the secondary veil, or velum, may be seen as a firm, felted or interwoven membrane stretched between the upper part of the stem and the edge or margin of the cap.
This particular type of mushroom starts out enclosed in what they call a universal veil that leaves a cup at the stem base.