Source : Webster's Revised Unabridged Dictionary (1913)

Ligneous \Lig"ne*ous\ (l[i^]g"n[-e]*[u^]s), a. [L. ligneus, fr.
   lignum wood. Cf. {Lignous}.]
   Made of wood; consisting of wood; of the nature of, or
   resembling, wood; woody.

         It should be tried with shoots of vines and roots of
         red roses; for it may be they, being of a moreligneous
         nature, will incorporate with the tree itself. --Bacon.

   {Ligneous marble}, wood coated or prepared so as to resemble
      marble.

Source : WordNet®

ligneous
     adj : consisting of or containing lignin or xylem; "ligneous (or
           woody) tissue"