The lichenRoccella montagnei collected in Waltair has been found to differ markedly in composition, depending upon the season. Erythrin, Erythritol, Lecanoric acid, Roccellic acid and Orcinol are the main components besides isolichenin. The present findings differ from previous work in that erythritol and roccellic acid are now found in this lichen whereas oxyroccellic acid is absent. The constitution of erythrin as the erythrityl ether of lecanoric acid is supported.