orchal

from The Collaborative International Dictionary of English v.0.48

Archil \Ar"chil\ (?; 277), n. [OF. orchel, orcheil, It. orcella,
   oricello, or OSp. orchillo. Cf. {Orchil}.]
   1. A violet dye obtained from several species of lichen
      ({Roccella tinctoria}, etc.), which grow on maritime rocks
      in the Canary and Cape Verd Islands, etc. --Tomlinson.
      [1913 Webster]

   2. The plant from which the dye is obtained. [Written also
      {orchal} and {orchil}.]
      [1913 Webster]