Parmotrema crinitum (Ach.) M. Choisy
Parmelia crinita Ach.
Thallus foliose, loosely attached to the substratum, to 15 cm across, lobes to 1-1.5 cm wide, margins sometimes indented, tips rounded, upper surface and margins with numerous black cilia, 2-5 mm long and numerous cylindrical or coralloid isidia, notably towards the center, grey-glaucous, grey-greeenish, pale grey-blue, but sometimes pale yellowish, see: Parmotrema crinitum forme saxicole jaunâtre; lower surface with simple rhizines, dark brown towards the margin, center darker. Apothecia rare, 3-8 mm diam., sessile or more or less stalked, disc brown, exciple crenulate and isidiate. Ascospores colourless, simple, broadly ellipsoid, slightly curved, 21-31 x 11-15 µm. Cortex: C-, K+ yellow, KC-, P-; medulla: C-, K+ yellow to orange, KC+ yellow-orange, P+ yellow-orange; UV-.. Strong maritime trends, and consequently often found on mossy trunks in oceanic woodlands, and also rather frequently, although localized, on rocks (or at their base in heathland) in the aerohaline zone, see: Parmotrema crinitum forme saxicole jaunätre.
N.B. Not to be confused with Parmelinopsis horrescens which is smaller, medulla K+ yellow, and with smaller lobes, less indented but with more abundant isidia.