The Collaborative International Dictionary of English v.0.48:

Orcin \Or"cin\, n. [Etymology uncertain: cf. F. orcine.] (Chem.)
   A colorless crystalline substance, C6H3.CH3.(OH)2, which is
   obtained from certain lichens (Roccella, Lecanora, etc.),
   also from extract of aloes, and artificially from certain
   derivatives of toluene. It changes readily into orcein.
   [1913 Webster]

WordNet (r) 3.0 (2006):

roccella
    n 1: a source of the dye archil and of litmus [syn: roccella,
         Roccella tinctoria]