The Collaborative International Dictionary of English v.0.48:

Lithophyte \Lith"o*phyte\, n. [Litho- + Gr. ? plant: cf. F.
   lithophyte.] (Zool.)
   A hard, or stony, plantlike organism, as the gorgonians,
   corals, and corallines, esp. those gorgonians having a
   calcareous axis. All the lithophytes except the corallines
   are animals.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lithophyte
    n 1: plant that grows on rocks or stony soil and derives
         nourishment from the atmosphere [syn: lithophyte,
         lithophytic plant]