Opegrapha atra

Whitish or green-grey thallus, the short (1 mm), prominent lirellae with black looking central slit often densely crowded at centre of thallus.

Common on the trunks, branches and twigs of trees with smooth shaded bark, rarely found on fences. Forms extensive mosaics on young trees but tends to avoid nutrient-enriched bark.

All year round.

Widespread and fairly frequent in Britain.

Fairly frequent in Leicestershire and Rutland.