Hypogymnia  

Thallus foliose, attached by adhesive discs below, or rarely by most of the lower cortex. Lobes inflated, often tubular, solid or ± hollow. Upper surface corticate, grey or suffused brown, often with soredia or pustules, lacking isidia and pseudocyphellae. Medulla white, solid or hollow, hyphae loosely woven, arachnoid or absent. Lower surface black, corticate, shiny, wrinkled, without rhizines, sometimes with gaping perforations. Photobiont chlorococcoid.
Anamorph: conidiomata pycnidial, common in fertile species, minute and punctiform, immersed and blackened around the ostiole. Conidia 5-8 × 1 μm, weakly bifusiform to cylindrical.
Teleomorph: ascomata apothecia, sessile or prominently stalked; disc shining, concave to flat, red- to yellow-brown; thalline exciple well-developed, persistent, concolorous, becoming torn. Asci 8-spored. Ascospores 3.5-10 × 3-6.5 μm, globose to shortly ellipsoidal, aseptate, hyaline.
Chemistry: cortex: atranorin and usnic acid in some species; medulla: β-orcinol depsides and orcinol and β-orcinol depsidones.