The Collaborative International Dictionary of English v.0.48:

Dryas \Dry"as\, n.; pl. Dryades. [L. See Dryad.] (Class.
   Myth.)
   A dryad.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Dryas
    n 1: mountain avens [syn: Dryas, genus Dryas]