The Collaborative International Dictionary of English v.0.48:

Antitropal \An*tit"ro*pal\, Antitropous \An*tit"ro*pous\, a.
   [Pref. anti- + Gr. ? turn, ? to turn.] (Bot.)
   At the extremity most remote from the hilum, as the embryo,
   or inverted with respect to the seed, as the radicle.
   --Lindley.
   [1913 Webster]