Life Habit: lichenized, not lichenicolous diaspores: as soredia (often as consoredia photobiont: primary one a trebouxioid green alga, secondary one absent; algal layer: usually indistinct or absent, when present horizontally discontinuous Ascomata and Conidiomata: absent Geography: world-wide, highest diversity probably in cool-temperate and boreal areas Substrate: on soil, rock, mosses, wood, bark, and over other lichens. Notes: In species forming rosettes, specimens may become contiguous obscuring marginal characters of individual thalli. Substances such, as fumarprotocetraric acid, stictic acid and atranorin, may occur in too low concentrations to allow for their detection by color reagents. Thus, TLC is necessary for a conclusive identification of most of the species and (chemotypes), although it is not possible to distinguish angardianic acid and roccellic acid by TLC (Leuckert et al. 1995). Spot tests: thallus K- or + yellow, C-, KC-, P- Substrate and ecology: on sun-exposed to shaded rocks (mainly sandstones, often vertical faces), on mosses over rocks, and on mosses over shaded bark (e.g., Quercus) World distribution: Europe and North America Sonoran distribution: Arizona at 1450-3000 m. Note: Lepraria borealis is morphologically similar to L. caesioalba, but according to Ekman and Třnsberg (2002) it is distinct from L. caesioalba s. str.