Hypocenomyce scalaris (Ach. ex Lilj.) M. Choisy

    Thallus squamulose, made of numerous scaly squamules distributed regularly, more or less intricated, 1-2.5 mm wide, squamules convex (like fingernails) with margin round, slightly rolled-up, swollen or crenulate with farinose soredia, green-yellowish, upper surface grey-greenish when moist, grey-brown to ochreaceous when dry, lower surface brown-yellowish, pale grey-greenish. Apothecia very rare, 1-2 mm diam., disc flat, black, sometimes powdered with bluish gray, exciple paler, more or less wavy, sometimes sorediate. Ascospores fusiform, simple, 7-8 x 3-4 µm. Photobiont: chlorococcoid. C+ red, K-, KC+ red, Pd-. A fairly rare species in our prospecting region because it has mountainous tendencies, on acid bark of trees, notably coniferous, but also timber and poles, rare on rocks.