The Collaborative International Dictionary of English v.0.48:

Heterogamous \Het`er*og"a*mous\, a. [Hetero- + Gr. ga`mos
   marriage: cf. F. h['e]t['e]rogame.] (Bot. & Biol.)
   (a) The condition of having two or more kinds of flowers
       which differ in regard to stamens and pistils, as in the
       aster.
   (b) Characterized by heterogamy.
       [1913 Webster]