Stereocaulon dactylophyllum Flörke

    Primary thallus squamulose, soon disappearing, secondary thallus forming small cushions, consisting of more or less erect pseudopodetia, 2-4 cm tall, grey-greenish when moist, greyish when dry, covered with numerous granular to squamulose small protuberances (phyllocladia), 1-2 mm, coralloid (coral branch shaped) or digitated, presence of cephalodia, crust forming, grey-brownish, 0.2-0.5 mm, harbouring the photobiont: Stigonema. Apothecia usually numerous at apices of small lateral branches, 1-2 mm diam., disc flat then slightly convex, brown-red when moist, blackish when dry, exciple thin and distinct, paler (beret-like). Ascospores thinly elongate, 3-7-septate, 20-36 x 3-4 µm. Photobiont: Trebouxioid. C-, K+ yellow, KC-, Pd+ yellow-orange to orange. Not especially maritime, common on rocks, notably schists near the seashore and inland, frequent also on shaded and damp roofs covered with thick old slates, traditional in Brittany, see : Stereocaulon dactylophyllum forme sur ardoises de toit.