The lichen Parmotrema cetratum contains traces of the unusual threitol
and unexpected volemitol, along with galactose (2%). Present is a com
plex containing a lightly branched beta-glucan containing (1-->3)- and
(1-->4)-linkages in a 25:47 molar ratio chemically linked to a galact
omannan with structural features common in other lichens. A glucogalac
tomannan with a small proportion of Glcrho side chains was also charac
terized.