Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, 2-9 cm in diam., adnate, subdichotomously to irregularly lobate lobes: irregular, elongate, +plane, separate, 1-5 mm wide, (50-)80-100(-150) µm thick; apices: rotund, entire to lobulate, occasionally upturned upper surface: bluish gray to medium gray, usually dull, smooth to somewhat roughened but not wrinkled, not isidiate internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 5-9 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale to medium gray, wrinkled, with scattered tufts of white hairs Apothecia: common, laminal, sessile to short stipitate, 0.2-2.5 mm wide disc: light brown to red-brown, concave to plane margin: thalline, concolorous with the thallus or cream-colored, entire or occastionally with microphylline outgrowths exciple: euparaplectenchymatous, often poorly developed centrally but up to 35 µm thick marginally hymenium: hyaline below and thinly brown above, 90-150 µm tall; paraphyses: unbranched, 1-2 µm wide, slightly inflated apically; subhymenium: yellow to pale brown, 35-70 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, submuriform, 3-5-septate transversely, 0-1-septate longitudinally, ellipsoid to subfusiform, 14-26 x 6-9 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on bark and sometimes acidic rocks World distribution: widespread, pantropical, extending into some temperate regions in North and South America, Australasia, Asia and Africa Sonoran distribution: Baja California Sur and Sinaloa. Notes: Leptogium azureum is a characteristically blue-gray, large-lobed species, which, when lobulate, may be confused with L. cyanescens, a thinner, more gray species with at least with some coralloid isidia, though sometimes also some lobules occur.