The ultraviolet and infrared spectral data for a number of lichen depsides, depsidones and their fission products have been recorded. The U.V. spectra of the orcinol depsides, orcinol depsidones andβ-orcinol depsidones are characteristic while those of theβ-orcinol depsides less useful for diagnostic purposes. The I.R. spectra are more useful and the carbonyl region is significant for this purpose.