The Collaborative International Dictionary of English v.0.48:

Dimerous \Dim"er*ous\, a. [Gr. di- = di`s- twice + ? part.]
   Composed of, or having, two parts of each kind.
   [1913 Webster]

   Note: A dimerous flower has two sepals, two petals, two
         stamens, and two pistils.
         [1913 Webster]