Description ²

 Thallus: continuous to fissured, with thin to moderately thick verrucae; margin: definite, often zonate; upper surface: whitish gray to greenish gray, margins entire to weakly zoned, epruinose; soredia: farinose, restricted to verrucae or coalescing and spreading onto ruptured thallus surface; Apothecia: no fertile specimens seen; Pycnidia: not seen; Spot tests: K- or K+ yellow to red, C-, KC+ rose-violet, P- or + yellow to red, UV-; Secondary metabolites: picrolichenic and ± protocetraric acids (both major); ± conprotocetraric and subpicrolichenic acid (both minor).; Substrate and ecology: on deciduous trees, such as Aesculus, Quercus or conifers, and also occasionally on siliceous rocks in shady places; World distribution: widely distributed in the Northern Hemisphere; Sonoran distribution: in coastal areas of southern California and Baja California and scattered in inland mountains up to 1800 m in Arizona and Chihuahua.; Notes: Pertusaria amara is characterized by small, but coalescing soralia with farinose soredia, a relatively thin, grayish thallus and the presence of the picrolichenic acid chemosyndrome and thus a bitter taste. It is hardly confused with any other Pertusaria species occurring in western North America, except P. albescens. The distinction of both species is discussed above. 

Sources and Credits

1. (c) CALS, some rights reserved (CC BY-NC-ND), uploaded by CALS
2. (c) Lichen Unlimited: Arizona State University, Tempe., some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/10547711

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