Hypotrachyna horrescens (Taylor) Krog & Swinscow forme corticole.
Parmelia horrescens Taylor
Parmelinopsis horrescens (Taylor) Elix & Hale
Thallus appressed, more or less regular rosette-like, 2-7 cm diam., made of lobes, truncated, markedly indented, 2-3 mm wide, upper surface pale grey when dry, grey-green to glaucous when moist, sometimes with brownish margins, covered with abundant isidia, concolourous or darker, cylindrical, swollen or rounded, sometimes coralloid, potentially covering the whole thallus, some isidia presenting simple cilia arising from their base, black, lower surface blackish, brown-black with simple rhizines. Apothecia very scarce, sessile, 2-4 mm diam., disc concave, dark brown-reddish, exciple indented to ciliate/isidiate. Ascospores shortly ellipsoid, 12-15 x 9-11 µm. Cortex : K+ yellow; medulla: C-, K-, KC+ dark pink, Pd-. Species occurring on tree bark in humid oceanic woods (Pinus, etc.) or sometimes on rocks in oceanic forests, see: Hypotrachyna horrescens forme saxicole des forêts océaniques, and in our prospecting area, on, or at the foot of the rocks of the aerohaline zone or on the rocks of the cliffs, see Hypotrachyna horrescens forme saxicole maritime. Not especially coastal, might be confused with Hypotrachyna minarum of which medulla is C+ pink, devoid of cilia arising from isidia on the lobe upper surface. Not to be confused with Parmotrema crinitum of which the lobes are much larger, less indented and with medulla K+ orange, Pd+ yellow-orange, and also much less isidia.