Evernia prunastri (L.) Ach. var. prunastri
Thallus apparently fruticose, anatomically foliose, small bush forming, 3-6 cm long, lobes rather soft in general pendent, strap-shaped, branched, with tips palmated, with mostly towards the margin non-delimited farinose soralia, oval to circular (sometimes very numerous, see Evernia prunastri forma), upper surface green-grey to pale green-yellow, often with an incomplete network of elongate ridges, lower surface minutely cannulated, whitish. Apothecia very rare, on top of stipe, 2-5 mm diam., disc brownish, exciple thin soon disappearing. Pycnidia frequent. Utriform asci, 30-35 x 16-20 µm according to our measurements, with 8 spores. Simple colorless spores, largely elliptical to globular, 7-11 x 4-6 µm according to the literature, 7-10 x 5-6 µm according to our measurements. Photobiont: chlorococcoid. Cortex: C-, K+ yellow on both faces, KC-, Pd-; medulla: C-, K-, KC-, Pd-. Widespread all over deciduous trees, notably branches and twigs, more scarce on coniferous in our prospection area, and very rare on soils (see Evernia prunastri var. arenaria) and on rocks (see Evernia prunastri var. prunastri on rock) . Easily confused with some Ramalina species of which the straps have the same colours on both faces but more stiff. There is one taxon lacking usnic acid, very pale grey: see Evernia prunastri f. herinii. N.B. The thallus of this species has a fruticose appearance but it is actually foliose due to the structure of its branches.
N.B. This species supports a relative pollution and can sometimes grow on artificial supports in more or less polluted zones, see: Evernia prunastri forme sur substrats artificiels.