Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, continuous to scurfy, often rimose-cracked, stratified with a distinct medulla or not stratified, delimited; prothallus: white, felty surface: silver-gray to dark gray, or greenish white to creamy white, corticate, arachnoid-byssoid, or powdery, sorediate or esorediate photobiont: primary one a green alga, secondary photobiont absent Ascomata: apothecial, round, 1(-3) immersed in thalline verrucae disc: black to brown, usually white pruinose margin: irregularly crenate or indistinct exciple: indistinct to poorly developed epihymenium: yellow, brown to dark brown-black, up to 90 µm thick, densely inspersed with crystals hymenium: colorless to pale straw, up to 310 µm tall; hypothecium colorless, of densely interwoven hyphae, up to 110 µm tall, sometimes not evident; paraphyses: mostly simple, but slightly branched and anastomosed in uppermost part, conglutinated or not, filiform; apical cell: only slightly swollen asci: broadly clavate to cylindrical-ellipsoid, with an indistinctly to distinctly thickened apex and I- tholus but I+ blue outer sheet, 1-8 spored ascospores: hyaline, or smoky gray or pale yellow when old, muriform, with or without apiculae, up to 305 x 75 µm Conidiomata: pycnidial; conidiogenous cells simple conidia: short, bacilliform Secondary metabolites: depsidones Geography: Africa, Asia, Europe, North America, South America, Australia (mainly a Southern Hemispheric genus) Substrate: bark, corticolous bryophytes, occasionally over bark and on rocks. Note: Originally Phlyctis was described as a section of Peltigera (Basionym: Peltigera sect. Phlyctis Wallr., Fl. Crypt. Germ.: 3: 553 [1831]), which is a foliose genus with hardly any characters in common.