pentamerous

from WordNet (r) 3.0 (2006)

pentamerous
    adj 1: divided into five parts; specifically, having each floral
           whorl consist of five (or a multiple of five) members;
           "pentamerous flowers"

from The Collaborative International Dictionary of English v.0.48

Pentamerous \Pen*tam"er*ous\, a. [Penta- + Gr. ? part.]
   1. (Biol.) Divided into, or consisting of, five parts; also,
      arranged in sets, with five parts in each set, as a flower
      with five sepals, five petals, five, or twice five,
      stamens, and five pistils.
      [1913 Webster]

   2. (Zool.) Belonging to the Pentamera.
      [1913 Webster]