thallus_surface_pruinose
pruina|<lobe> pruina
upper surface gray to gray-white, finely maculate, smooth to more or less warty in older parts, usually epruinose but rarely with faint pruina on some lobe ends; lower surface white to off-white, occasionally slight dingy gray in parts, flat (especially in prostrate form) to distinctly concave (canaliculate) in more ascendant forms
Physcia rhizinata
Physcia rhizinata