The Collaborative International Dictionary of English v.0.48:

Adversifoliate \Ad*ver`si*fo"li*ate\, Adversifolious
\Ad*ver`si*fo"li*ous\a. [L. adversus opposite + folium leaf.]
   (Bot.)
   Having opposite leaves, as plants which have the leaves so
   arranged on the stem.
   [1913 Webster]