Physconia grisea (Lam.) Poelt
Thallus foliose, more or less rosette-shaped, 5-8 cm diam., tightly appressed to the substratum, composed of lobes, 1-2 mm wide, radiating and partly overlapping, upper surface markedly spotted pruinose, whitish, conspicuous towards the margins, spots possibly contiguous in the center, overall aspect pale greyish, pale grey-brownish when dry, bronze to brown-greenish when moist, markedly green when rainy or rehydrated, covered notably towards the center with granular isidia and sorelia, grey-greeenish, lower surface whitish, darker in the center, simple rhizines, whitish to pale ochre. Apothecia very rare, more or less sessile, 1-3 mm diam., disc brown-red, pruinose, thalline exciple sorediate. Ascospores brown, thick walls, minutely dotted, 22-34 x 12-17 µm. Pycnidia frequent. Cortex: K-; medulla (white): K-. On nutrient-enriched bark of deciduous tree trunks in parklands or isolate, also on rocks and walls provided that the substratum is neutral or alkaline. Not to be confused with Physconia perisidiosa a of which the rhizines are bottle-brush-shaped and with Physconia enteroxantha which has a yellow medulla.