The Collaborative International Dictionary of English v.0.48:

Orthotropal \Or*thot"ro*pal\, Orthotropous \Or*thot"ro*pous\, a.
   [Ortho- + Gr. ? to turn: cf. F. orthotrope.] (Bot.)
   Having the axis of an ovule or seed straight from the hilum
   and chalaza to the orifice or the micropyle; atropous.
   [1913 Webster]

   Note: This word has also been used (but improperly) to
         describe any embryo whose radicle points towards, or is
         next to, the hilum.
         [1913 Webster]

WordNet (r) 3.0 (2006):

orthotropous
    adj 1: (of a plant ovule) completely straight with the micropyle
           at the apex [ant: campylotropous]