The Collaborative International Dictionary of English v.0.48:

Rhatany \Rhat"a*ny\, Rhatanhy \Rhat"an*hy\, n. [Sp. ratania,
   rata[~n]a, Peruv. rata[~n]a.]
   The powerfully astringent root of a half-shrubby Peruvian
   plant (Krameria triandra). It is used in medicine and to
   color port wine. [Written also ratany.]
   [1913 Webster]

   Savanilla rhatany, the root of Krameria Ixina, a native
      of New Granada.
      [1913 Webster]