Hypogymnia farinacea Zopf.
Hypogymnia bitteriana (Zahlbr.) Räsänen
Thallus foliose, spreading, forming rosettes, to 3-10 cm diam., lobes 1-3 mm wide, convex, hollow but flattened towards the apices, contiguous to overlapping, upper surface more or less wrinkled, notably towards the center, pale greyish, grey-bluish when dry, pale grey-greenish when moist, covered towards the center with small isidioid folds or coarse-textured with large soralia more or less aggregated that may extend to the whole thallus, grey-yellowish, grey-greenish; lower surface without rhizines, black. Apothecia very rare, more or less stalked, 3-5 mm diam., disc concave, brown-redish. Ascospores simple, colourless, subglobose, 5-6 x 4-5 µm. Photobiont: chlorococcoid. Medulla : C-, K-, KC+/- red-orange, Pd-; cortex : C-, K+ yellow, KC-, Pd+ pale yellow; soralia : K+ yellow > redish, KC+ yellow > redish. Rare, on acid bark of deciduous trees and coniferous, and also on acid rocks. See Hypogymnia physodes of which the medulla is Pd+ red and soralia exclusively lip-shaped and Parmeliopsis ambigua that most often is R-, has rhizines and soralia not wrinkled.*