English: A lichen - Evernia prunastri. A common name for this species is "Oak Moss", although it is not a moss, nor is it confined to Oak trees. The specimen in this photograph was growing on the bark of a tree that stands beside a footpath leading to Overtoun House.

This is a fairly common species on trees, and it is quite tolerant of air pollution. Though somewhat similar to Ramalina farinacea, its branches have a paler underside, a feature that is visible in this photograph (see also 1073623). Another similar species is Pseudevernia furfuracea: 1073683.

In some countries, E. prunastri and P. furfuracea are economically important species: "The perfume industry uses lichens in large quantities, chiefly oak moss Evernia prunastri (L.) Ach. and tree moss Pseudevernia furfuracea (L.) Zopf, thousands of tons of which are collected from trees in the forests of France, Yugoslavia, and Morocco" [Jack R. Laundon, in "Lichens" (Shire Natural History)].

Other diverse uses for this species, as listed by Frank S. Dobson in "Lichens - An Illustrated Guide to the British and Irish Species", include: a flavouring for bread in the Middle East; wadding in shotguns; and a nest-building material that is favoured by long-tailed tits. The same work notes that "the usnic acid it contains can be used to produce an antibiotic but it has also been known to produce an allergy in woodcutters".