Usnea flammea Stirt. forme saxicole.

    Thallus tufted, to 6 (or more) cm tall, more often pendulous or slightly erect, flexible, yellow-greenish, greenish, main branches wavy more or less intertwined with pale annular cracks or rings, base not blackened, surface smooth with a few warts or papillae except sometimes towards the base, medulla more or less flexible, secondary branches thin, originating most often from the same side as the main branches and with apices of both main and secondary branches ending at the same evel, minutely isidiate and even more or less sorediate. Infertile, Photobiont: trebouxioid. Thallus : C-, K+ yellow or sometimes blood-red, Pd+ yellow-orange. Medulla : K+ yellow>red, Pd+ orange. On siliceous rocks of vertical walls exposed to winds in the aerohaline zone, but also on rocks of schist ridges in the Arrée Mounts. Species occurring on the windy siliceous rocks of the aerohaline zone, most often on the vertical faces but also on the rocks of the schistose ridges of the Monts d'Arrée (but see Usnea schadenbergiana rather similar), also, but less frequently on tree bark, see: Usnea flammea forme corticole. N.B. In the heathlands of the windy and very exposed Caps, watch out for Usnea subscabrosa with branches very finely punctuated with soralia or isidiomorphs and which most often comes to the ground at the foot of the rocks or in low vegetation.