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

Thallus: crustose with a leprose surface, irregular, indeterminate, without a distinct margin, continuous, well fastened to the substrate, without lobes, up to 0.4 mm thick upper surface: external soredia yellow, eroded patches showing white soredia and/or a white medulla soredia: coarse, fluffy, up to 0.1 mm in diam.; projecting hyphae indistinct or absent medulla: distinct, white lower surface: not evident or as loose weft of hyphae, without a distinct tomentum Spot tests: K+ slowly orange, C-, KC-, P+ brownish red Secondary metabolites: 4-oxypannaric acid-2-methyl ester (major), 4-oxypannaric acid (minor), pannaric acid (tr.), and pannaric acid-2-methyl ester (tr.) Substrate and ecology: on mosses on rocky cliff World distribution: Europe and North America Sonoran distribution: southern California. Note: The Sonoran material belongs to L. diffusum var. chrysodetoides (J.R. Laundon) Kukwa, Ann. Bot. Fennici