The Collaborative International Dictionary of English v.0.48:

Conhydrine \Con*hy"drine\ (? or ?), n. [Conium + hydrate.]
   (Chem.)
   A vegetable alkaloid found with conine in the poison hemlock
   (Conium maculatum). It is a white crystalline substance,
   C8H17NO, easily convertible into conine.
   [1913 Webster]