Abstract
A new delimitation of the lichen genus Psora Hoffm. is proposed. The genus is mainly characterized by a squamulose thallus, an upper cortex of ‘Scheinrindentyp’, a hypothecium containing calcium oxalate, an amyloid hymenium containing anthra–quinones, the type of ascus and the type of pycnidium. The affinities of Psora to the genera Eremastrella, Psorula, and Xanthopsora and some squamulose species provisionally included in Lecidea are discussed. The genus Chrysopsora is reduced to syn–onomy with Psora, and the species Lecidea hedinii, L. scholanderi, and Psora petri to synonomy with Lecidea pulcherrima, Toninia tristis, and Lecidea lurida, respectively. The new combinations Lecanora scotopholis (Tuck.) Timdal, Psora hypotheja (Lamb) Timdal, P. subrubiformis (Vainio) Timdal, and P. vallesiaca (Schaerer) Timdal are proposed.New chemical data are given for a number of the species and chemical strains are recognized for the first time in Psora crenala, P. globifera, P. gresinonis, and P. rubifor–mis. Two new chemical strains of P. decipiens are recorded.
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