Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: erect-shrubby, short, 1.5-5 cm long branching: anisotomic dichotomous, divergent basal part: concolorous to branches or pale brown to brownish black branches: cylindrical to irregular, swollen or fusiform, lateral branches distinctly to not narrowed at point of attachement; foveoles or transversal furrows: present or absent segments: terete, cylindrical to strongly sausage-like papillae: nearly absent to numerous, irregularly distributed on main branches fibercles: absent to few fibrils: short (1-2 mm) and slender, few to numerous, irregularly distributed on branches, giving sometimes a spinulous aspect to the branches soralia: usually numerous, as large or larger than half the diameter of the branch, convex, plane or slightly excavate, developing initially on the cortex or at the top of eroded tubercles, especially at the apical part of the branches, fusing together and often covering entirely the apices isidiomorphs: present on young soralia, rarely on mature ones cortex: thin (5-8%), shiny, with minute purple red spots (sometimes absent or rare) medulla: thin to most frequently thick, usually two layered: compact close to the cortex and lax around the axis, sometimes pale yellow peripherally axis: thin to thick, unpigmented or yellowish orange to pale orange (especially at the apices) Apothecia: not seen Spot tests: K+ intense yellow, C+ intense yellow, KC+ intense yellow, P+ orang-ish, or K-, C-, KC-, P- Secondary metabolites: fatty acids, or norstictic ±fatty acids, or none detected. Substrate and ecology: on bark or rock, rarely on wood, mainly coastal between 200 and 800 m, on Quercus spp., Pinus spp. and diverse scrubs in Quercus woodland, Quercus forests or in the chaparral World distribution: Europe, North Africa, North and South America, Macaronesia Sonoran distribution: common on the Channel Islands and mainland of southern California and scattered in coastal Baja California. Notes: In eastern North America the red dots covering the cortex are diagnostic for U. flavocardia. Usnea brattiae may also have some red spots on the cortex as well, but these are very localized on some of the papillae.