The first FT-Raman spectroscopic study of foliicolous lichens is reported. Detailed spectra obtained by macroscopic and microscopic means for Calenia triseptata Zahlbr., Echinoplaca strigulacea (Müll. Arg.) R.Sant. and Tricharia carnea (Müll. Arg.) R.Sant. collected from Costa Rican rainforests have been interpreted mainly in terms of their xalate content. The Raman spectra show a significant presence of calcium oxalate monohydrate (whewellite) despite the lack of calcium ions available in the leaf itself. A reasonable explanation for its presence could be the result of the incorporation of calcium ions from airborne dust and/or dissolved in rain falling on the canopy.
