Caloplaca obscurella. This species is well named because it is seriously obscure. The apothecia are very small and can only really be found using a handlens, and look more as if they belong to the genus Lecania. Once again, confirmation by looking at the spores is essential. It is usually found on trees with a relatively basic bark such as poplar of ash. Although hard to spot, it is a relatively common species. This photograph was taken at Kingcombe in Dorset.