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 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. 


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© Lichen Unlimited: Arizona State University, Tempe.

Source: Lichen Flora of the Greater Sonoran Desert Region

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