Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Life habit: lichenized Thallus: foliose, lobate lobes: radiating, but sometimes irregular; lobe tips: usually rotund, eciliate upper surface: white, whitish gray to brownish-gray, leaden to bluish gray or stramineous, ± plane to convex or concave towards the periphery, sometimes reticulately ridged, shiny or dull, usually pruinose; with or without soralia, polysidiangia (= pustulate isidia) or isidia; pseudocyphellae: present in most species upper cortex: paraplectenchymatous, formed by vertically arranged hyphae medulla: separated into upper and lower layers, which are very often of different color and show different chemical reactions photobiont: primary one a Trebouxia, secondary photobiont absent lower cortex: prosoplectenchymatous, formed by longitudinally arranged hyphae lower surface: usually black, whitish, brownish or bluish peripherally; attachment: by simple to multiple, furcately divided rhizines; cyphellae, pseudocyphellae and tomentum absent Ascomata: apothecial, laminal, orbicular, sessile to elevated on a distinct internal stipe; thalline margin: prominent or reflexed, either distinct and persistent (physciaeformis-type), or in young apothecia distinct, then vanishing and giving the apothecia a lecideine appearance (cocoes-type), or lacking such that all apothecia have a lecideine appearance from the beginning (obscurascens-type); exciple: present and persistent, sometimes blackened and/or substituted by a thickening parathecium; epithecium: bluish-black, K+ purple; hypothecium: brown asci: lecanoral, with thickened apex wall layers (apex I+ blue), with distinct axial body, 8-spored ascospores: brown, 1-3-septate, thick-walled, mischoblastiomorphic, ellipsoid, 10-23 µm x 4-8 µm Conidiomata: usually present, pycnidial, laminal, immersed, conidiophore-type VI (Vobis 1980) conidia: ± bacilliform, formed pleurogenously, 3-4 x 0.8-1.2 µm Secondary metabolites: upper cortex with atranorin and chloroatranorin) or lichexanthone, seldom (only in P. nubila) without acetone-soluble substances; medulla usually with terpenes and pigments [in old-world and Australasian species with norstictic acid (incl. satellites) often present], testacein (Rf-values: A 42, B' 25, C 20, pinkish after treatment with sulfuric acid and heat), a compound first detected in Parmelia testacea and of unknown structure and substance class present in some species Geography: predominately tropical and subtropical with few species extending to temperate regions Substrate: mostly bark, acidic rocks or mosses.