Volva

from WordNet (r) 3.0 (2006)

volva
    n 1: cuplike structure around the base of the stalk of certain
         fungi

from The Collaborative International Dictionary of English v.0.48

Volva \Vol"va\, n. [L. volva, vulva, covering.] (Bot.)
   A saclike envelope of certain fungi, which bursts open as the
   plant develops.
   [1913 Webster]