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 to subfruticose, lobate, separate, loosely imbricate lobes: linear-elongate, canaliculate; apices: usually truncate, ciliate upper surface: light gray to gray, smooth, plane to rugulose, shiny or matt, maculate or not, usually epruinose; with or without isidia or soredia; pseudocyphellae absent upper cortex: thin, c. 30 µm thick; pored epicortex, paraplectenchymatous medulla: white, loosely packed, cell walls containing isolichenan photobionts: primary one a Trebouxia, secondary photobiont absent lower surface: brown to black, rhizinate or not; rhizines: long, simple, sparse, concolorous; cyphellae, pseudocyphellae and tomentum absent Apothecia: laminal on thallus, orbicular, cup-shaped, subpedicellate or pedicellate; stipe: hollow; margin: prominent with thalloid rim; disc: imperforate, brown to dark brown; exciple: gray or hyaline; epithecium: brown or brownish yellow; hypothecium: hyaline asci: lecanoral, wall layers of apex thickened, apex amyloid, relatively large (mean of 50 x 23 µm), c. 8-spored ascospores: simple, ellipsoid; 10-28 x 4-12 µm; walls: thin, hyaline, not amyloid Conidiomata: pycnidial, laminal or marginal, immersed or emergent sessile conidia: bifusiform, 4-10 x 1 µm, or rarely filiform, 13-21 x 1 µm Secondary metabolites: upper cortex atranorin and chloroatranorin; medulla some combination of orcinol depsides or depsidones, ß-orcinol depsides or depsidones, benzyl esters, or aliphatic acids Geography: pantropical and extending into subtropical, montane regions, most diverse in Central and South America Substrate: mostly bark, particularly common on conifers, rarely on rock. Notes: The use of paraplectenchymatous to describe the upper cortex follows the use of that term by Hale (e.g. see Elix 1993a), but Culberson and Culberson (1981) designated it prosoplechtenchymatous. Because of the relative sparsity of true rhizines, the marginal cilia may sometimes touch the substrate, and consequently some authors have referred them as marginal rhizines. The related genus Cetrariastrum (not in the Sonoran region) has irregularly branched lobes, apothecia with solid stalks, smaller asci and a thicker hypothecium. Within the Sonoran region the only confusable genus is Pseudevernia, that lacks cilia entirely, has smaller ascospores and contains Cetraria-type lichenan in the hyphae cell walls.