Candelaria concolor. This species is so similar to members of Xanthoria, that I thought  should attend to it now. Unlike any Xanthoria, it is K- and not K+ purple. It is a true yellow, with no hint of orange, and lacks any granules or blastidia. It is a common species on basic barked trees and here, unusually, it is fertile. This photograph was taken on a fine avenue of black poplars in Gorey, Jersey.