Phytologia 28: 483 (1974).
Basionym: Lichen tiliaceus Hoffm., Enum. critic. lich. europ. (Bern): 96 (1784).
Thallus: foliose, adnate, more or less rosette-forming, to 15 cm diam., irregularly branched, pale grey. Lobes sublinear, often imbricate, apically rounded, partly pruinose, to 8 mm wide, ciliate; cilia black, to 0.7 mm long; isidia very common, cylindrical, little-branched, short and broad, blackened at tips. Lower surface black; rhizines black and simple, 1-2 mm long. Apothecia rare, sessile, rhizinate, to 4 mm diam.; disc brown. Spores ellipsoid, 8-11 x 5- 6 μm. Pycnidia black, immersed. Conidia slightly dumbbell-shaped, 5- 8 x 1 μm.
Photobiont: Data lacking.
Chemistry: Cortex C, K+ yellow, KC, PD; atranorin. Medulla C+ red, K, KC+ red, PD; lecanoric acid.
Ecology: On bark of deciduous trees, especially in nutrient-rich, open woodland areas, parks and along avenues, less common on rocks, but often abundant on maritime rocks (ornithocoprophilous), especially at its northern localities.
Distribution Type: Southem, reaching Central Norway, Central Sweden and SW Finland. Common in temperate and subtropical areas of Central and South Europe with continental tendencies, extending to Macaronesia, North Africa, Near East, and recently recorded across Russia to Far East and China.
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