General Description
Thallus light to medium grey, smooth or warted, often with a thin dark prothallus. Usually fertile, with the apothecia mainly in the more central part of the thallus. The apothecia are large, up to 3mm diameter. The black disc has a thick, notched grey margin. Cutting through an apothecium shows the dark purple interior.
Identification
Chemistry: Cortex K+ yellow, medulla UV+ ice blue.
Similar species: Easily confused with Lecanora gangaleoides but cutting through an apothecium of L. gangaleoides shows a pale green interior.
Habitats
On well-lit, siliceous rocks and walls, often on the run-off from mortar. Rarely found on trees.
Distribution Map
Distribution
Common throughout Britain and Ireland.
References
Text by David Brabban