SUMMARYFour natural products are reported as new to the two European species of the lichen genusPseudevernia. Pseudevernia furfuraceaproduces physodic acid, oxyphysodic acid, alectoronic acid, and, in some specimens, 2′-0-methylphysodic acid. Most specimens ofP. olivetorinaproduce olivetoric and 4-O-demethylmicraphyllinic acids, but a few also contain the secondary products ofP. furfuraceawith the exception of oxyphysodic acid. A simple biochemical scheme is proposed to explain the joint occurrences of these orcinol-type depsides and depsidones. In southwestern Sweden site-to-site and within-site comparisons of the proportions of the chemotypes on the same and on different substrates showed great variations, some significant differences, but no consistent correlations. If the chemotypes are indeed biologically distinct, their complex ecologies are controlled by factors exceeding those of substrate alone.