Phytologia 28: 335 (1974).

Basionym: Parmelia cetrata Ach., Syn. Lich.: 198 (1814).

Type locality: USA, Pennsylvania, Mühlenberg s.n. (H-ACH - lectotype; UPS - isolectotype). Designated by Hale & Fletcher 1990

Coordinates: 40°54'53"N, 77°46'29"W 40.914722, -77.774722

Thallus: foliose, membranaceous to somewhat coriaceous, medium grey to green-grey. Lobes up to 1.5 cm wide, rounded, crenate or deeply incised, the laciniae 1 - 3 mm wide, with truncate apices, ciliate, cilia 1 - 2 mm long. Upper cortex reticulately maculate and cracked. Medulla white. Under side smooth, black, with a dark brown marginal zone, densely rhizinate, often with rhizines and papillae to the margins, rhizines mainly simple, but occasionally squarrose. Isidia and soredia absent. Apothecia stipitate, thalline exciple entire, disc perforate. Spores 11 - 13 / 8 - 10 µm. Pycnoconidia filiform, 10 - 14 µm long (Swinscow & Krog 1988: 170, Hale & Fletcher 1990: 27). [Spores 13 - 15 / 7 - 9 µm] (Hale & Fletcher 1990: 27)

Algae: Trebouxioid green alga.

Chemistry: Atranorin (+), Salazinic acid (K+ red, PD+ orange), (Swinscow & Krog 1988: 170). Atranorin, chloratranorin, salacinic acid, consalacinic acid (Hale & Fletcher 1990: 27). Gyrophoric acid as an accessory substance (Moon et al. 2001: 323).

Ecology: Corticolous. In East Africa on well-lit, mist-affected hills at 1400 to 2600 m altitude, uncommon (Swinscow & Krog 1988: 170).

Molecular data: Genbank

Distribution: Pantemperate, pansubtropical, especially common in SE USA and Southern Africa. Kenya, Tanzania. Widely distributed in temperate, subtropical and tropical regions of North, Central and South America, Pacific regions and Africa.