Buellia griseovirens (Turner & Borrer ex Sm.) Almb.

A sorediate Buellia that rarely forms fruiting bodies with 3-septate ascospores (most members of the genus have only 1-septate ones). Characteristic are the yellowish, often depressed, delimited soralia; the surface soredia is usually grey or bluish. However, they may resemble various unrelated species (e.g. Xylographa vitiligo and Violella fucata), and also the rare B. arborea, from which B. griseovirens differs in secondary metabolites. It produces norstictic acid, whereas B. arborea contains atranorin and placodiolic acid. Norstictic acid is often present only in low concentrations in B. griseovirens and is barely detectable by the thallus reaction. Even the formation of red crystals after the addition of KOH in a microscopic sample may not always work reliably, so atypical specimens must usually be verified by TLC.

The species grows on trunks and branches of various deciduous and infrequently also coniferous trees, but often it is found on dead wood as well. It occurs in a wide range of forest habitats and also on solitary trees. It is widespread in Europe and abundant in most of its parts. In the Czech Republic, it is clearly the most abundant epiphytic genus member, occurring throughout the entire country from lowlands to mountains.

Ascomycota → Lecanoromycetes → Caliciales → Caliciaceae → Buellia