Pyrenula nitida (Weigel) Ach.

Quite an easily recognized pyrenocapous lichen characterized by a thick green-grey thallus with minute white pseudocyphellae. Perithecia are immersed in major part, up to 1 mm large and contain antraquinones in the wall (K+ purple in cross-section). The spores are more or less brown, 3-septate, thick-walled and lenticular.

Pyrenula nitida is a typical lichen on the smooth bark of older deciduous trees in forests from lowlands to mountains. It usually grows on trunks of beech and hornbeam, often near the bases, sometimes also in shaded cavities between the roots. In Europe, the species is widely distributed but more abundant only in natural areas with an abundance of old-growth forests. In the Czech Republic, it can be considered a good indicator of natural beech forests with continual development. It is more abundant, e.g., in the Šumava, Český les and Beskydy Mts, and in the Moravský kras (Moravian karst). In northern Bohemia, the lichen almost disappeared due to the effect of the acid rains in the past.

Ascomycota → Eurotiomycetes → Pyrenulales → Pyrenulaceae → Pyrenula