A grey or grey-brown lichen with lobes that widen towards the tips where they are covered in white crystals. The underside is pale brown, the rhizines generally pale. The lichen turns bright green when thoroughly wet. Coarse powdery granules develop on the margins of the lobes, sometimes appearing as short pegs. These can cover the entire surface in the centre of the thallus.
Chemistry: All reactions negative.
Similar species: Phaeophyscia orbicularis lacks the white crystals. Physconia enteroxantha is black beneath with dark rhizines, with a yellowish and K+ yellow medulla.
On trees and rocks with very high nutrient enrichment.
Throughout Britain and Ireland but more common in the south and east.
Text by Fay Newbery