Protoparmeliopsis muralis

General: Saxicolous placodioid lichen forming rosettes, well adapted to urban masonry and concrete, highly tolerant of atmospheric pollution; thallus greenish-grey with distinct radiating marginal lobes, and abundant central apothecia.

Apothecia: Disc-shaped, 0.5-1.5 mm diam., greenish-brown to cream or brown depending on hydration, K-.

Asci: Clavate, 30-45 x 9-14 µm, spores irregularly biseriate, lower half strongly amyloid in Melzer's reagent.

Paraphyses: Abundant, slender, hyaline, septate, 2-3 µm wide, unbranched, without apical inflations, slightly projecting above asci.

Ascospores: Ellipsoid, hyaline, smooth, thin- to moderately thick-walled, unicellular, 10-16 x 7-9 µm, containing lipid droplets.