The Collaborative International Dictionary of English v.0.48:

Hypocist \Hyp"o*cist\, n. [Gr. ? a plant growing on the roots of
   the Cistus.]
   An astringent inspissated juice obtained from the fruit of a
   plant (Cytinus hypocistis), growing from the roots of the
   Cistus, a small European shrub.
   [1913 Webster]