The Collaborative International Dictionary of English v.0.48:

Alstonia \Alstonia\ n.
   1. 1 genus of evergreen trees or shrubs with white
      funnel-shaped flowers and milky sap; tropical Africa to
      southeast Asia and Polynesia.

   Syn: genus Alstonia.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Alstonia
    n 1: genus of evergreen trees or shrubs with white funnel-shaped
         flowers and milky sap; tropical Africa to southeastern Asia
         and Polynesia [syn: Alstonia, genus Alstonia]