The Collaborative International Dictionary of English v.0.48:

Omphalode \Om"pha*lode\, n. [Omphalo- + Gr. e'i^dos form.]
   (Bot.)
   The central part of the hilum of a seed, through which the
   nutrient vessels pass into the rhaphe or the chalaza; --
   called also omphalodium.
   [1913 Webster]