Phenology All year round.
A silvery grey-green Foliose lichen with dish like lobes. The lobes have a network of sharp ridges and depressions giving it a hammered or netted appearance. The yellow 'pustules' in the featured image are soralia.
Upper surface webbed with ridges and whitish pseudocyphellae (looks like hammered metal!)
Powdery soredia along ridges and lobe margins.
Lower surface black, densely covered in black rhizines which are simple on young lobes, becoming squarrose (branched like a bottle-brush) with age.
Pollution tolerant Usually on trees occasionally on rock.
IMAGE (C) 2014 Gordon Jackson