The Collaborative International Dictionary of English v.0.48:

Unicentral \U`ni*cen"tral\, a. [Uni- + central.] (Biol.)
   Having a single center of growth.
   [1913 Webster]

   Unicentral development, that form of development which
      takes place primarily around a single central point, as in
      the lowest of unicellular organisms.
      [1913 Webster]