Rhizocarpon distinctum Th. Fr.

The thallus of R. distinctum is dull, pale brown to grey, the black apothecia are almost round without a proper margin. Epithecium is K+ purple in a microscope slide. Spores are hyaline, 3-septate to submuriform. It is distinguished by an amyloid (I+ blue) medulla.

The species grows on slightly calcareous, nutrient-enriched or dusty silicates. It is common on various anthropogenic substrates, such as walls of natural rocks, bricks, roof tiles, granite gravestones, rock monuments or menhirs. It has a wide altitudinal amplitude. In the Czech Republic, it is one of the most common and abundant brown Rhizocarpon species.

Ascomycota → Lecanoromycetes → Rhizocarpales → Rhizocarpaceae → Rhizocarpon