Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, 2-7 cm in diam., adnate, irregularly lobate lobes: irregular, elongate, radiate, often anatomosing, strongly thickened (swelling markedly when wet), 1-4 mm wide, 125-500 µm thick; apices: rotund, thickened, entire or lobulate upper surface: greenish gray to medium gray, usually dull, heavily wrinkled longitudinally, not isidiate internal anatomy: with upper and lower cortices consisting of a single layer of irregularly isodiametrical cells 4-9 µm in diam., internally with loosely interwoven chains of Nostoc and hyphae lower surface: pale to greenish gray, wrinkled, with scattered tufts of white hairs Apothecia: common, often marginal, sessile, 0.5-3 mm wide disc: brown to red-brown, concave to plane margin: thalline, concolorous with the thallus, verrucose or heavily periclinally wrinkled exciple: euparaplectenchymatous, 70-115 µm thick centrally hymenium: hyaline below and thinly brown above, 105-140 µm tall; paraphyses: unbranched, 1-2 µm wide, slightly inflated apically; subhymenium: pale yellow, 25-125 µm thick asci: cylindrico-clavate, 8-spored ascospores: hyaline, muriform, 35-septate transversely, 0-1-septate longitudinally, ellipsoid to subfusiform, 20-30 x 9-12 µm Pycnidia: not observed Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: rare in the Sonoran region on bark of soft-barked oaks at intermediate elevations; elsewhere on a variety of deciduous trees World distribution: mostly subtropical to warm temperate, occurring in North America (Mexico and eastern U.S.A.) and South America (Brazil) Sonoran distribution: infrequent in Arizona, western Chihuahua and Sinaloa. Notes: Leptogium chloromelum is a characteristic species only confusable with miscolored light specimens of L. phyllocarpum, which has different apothecia without a granulose margin. Leptogium millegranum is also habitually similar, but is covered in isidia and has therefore a more granular thallus.