Physcia

Upper Surface: K+ yellow (atranorin), paraplectenchymatous, often pruinose, occ. maculate, occ. ciliate
Lower Surface: corticate, generally white, either paraplectenchymatous or prosoplectenchymatous, unbranched short rhizines
Algae: green (trebouxioid)
Reproduction: either apothecia or soredia, rarely both, never isidia
Spores: physcioid (thick-walled, not Physconia-type)

Worldwide.

Common name: Rosette Lichens
Family: Physciaceae

Relatively small or narrow-lobed foliose lichens, typically light gray (“atranorin gray”) and dull.

Found on all types of substrates, though typically associated with nutrient enrichment, such as dusty regions, near feedlots, under bird perches, etc. Often found with Xanthoria spp.

Heterodermia: usually lacks lower cortex, upper cortex prosoplectenchymatous
Phaeophyscia and Physciella: upper cortex K-, generally darker, never pruinose
Physconia: rhizines squarrose or at least mostly branched, generally dark below
Parmeliaceae: shiny at least near growing tips, typically much larger, spores totally different

Indicator of eutrophic habitats. Often relatively pollution-tolerant.