universal veil

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mycology A thin layer of tissue which completely surrounds a developing mushroom.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun 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