mesocarp

from WordNet (r) 3.0 (2006)

mesocarp
    n 1: the middle layer of a pericarp

from The Collaborative International Dictionary of English v.0.48

Mesocarp \Mes"o*carp\, n. [Meso- + Gr. karpo`s fruit.] (Bot.)
   The middle layer of a pericarp which consists of three
   distinct or dissimilar layers. --Gray.
   [1913 Webster]