The Collaborative International Dictionary of English v.0.48:

Endogenous \En*dog"e*nous\, a.
   1. (Bot.) Increasing by internal growth and elongation at the
      summit, instead of externally, and having no distinction
      of pith, wood, and bark, as the rattan, the palm, the
      cornstalk.
      [1913 Webster]

   2. (Biol.) Originating from within; increasing by internal
      growth.
      [1913 Webster]

   Endogenous multiplication (Biol.), a method of cell
      formation, seen in cells having a cell wall. The nucleus
      and protoplasm divide into two distinct masses; these in
      turn become divided and subdivided, each division becoming
      a new cell, until finally the original cell wall is
      ruptured and the new cells are liberated (see
      Segmentation, and Illust. of Cell Division, under
      Division). This mode of growth is characteristic of many
      forms of cells, both animal and vegetable.
      [1913 Webster]

WordNet (r) 3.0 (2006):

endogenous
    adj 1: of or resembling an endogen
    2: derived or originating internally [syn: endogenous,
       endogenic] [ant: exogenic, exogenous]