The Collaborative International Dictionary of English v.0.48:

Atropa \Atropa\ n.
   a genus of plants of the nightshade family, including the
   belladonna (Atropa belladonna).

   Syn: genus Atropa.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Atropa
    n 1: belladonna [syn: Atropa, genus Atropa]