Physconia enteroxantha (Nyl.) Poelt

This species is characterized by a yellow KOH reaction of the medulla. The medulla and soralia are often also yellow due to the presence of the pigment secalonic acid A. However, in some specimens there are only low concentrations of the pigment and the KOH reaction is uncertain. In such cases, confusion with the rare boreal P. detersa, which has not been recently documented in the Czech Republic, is possible.

The lichen commonly occurs on trunks and branches of deciduous trees with higher bark pH in both forest and non-forest communities. It rarely also grows on (mossy) rocks. It is common and widely distributed in Europe and scattered to abundant from lowlands to mountains in the Czech Republic.

Ascomycota → Lecanoromycetes → Caliciales → Physciaceae → Physconia