The lichen Parmotrema cetratum contains traces of the unusual threitol and unexpected volemitol, along with galactose (2%). Present is a complex containing a lightly branched beta-glucan containing (1-->3) and (1-->4)-linkages in a 25:47 molar ratio chemically linked to a galactomannan with structural features common in other lichens. A glucogalactomannan with a small proportion of Glc rho side chains was also characterized.