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Common Name: The Bone Lichens. Stresses the hollow lobes of the species and the pale, often whitish, upper cortex.
Small to medium stratified foliose lichens, corticate above and below, sorediate or rarely isidiate or not, lobes rather loosely appressed to semi-erect or pendulous, hollow, occasionally perforate, 0.5–5 mm wide. Upper surface usually pale greyish, occasionally brownish. Lower surface blackish, shiny, wrinkled, lacking rhizines. Medulla white. Photobiont green.
Apothecia located over upper surface, often stalked/stipitate, disc usually concave, brown; spores simple, spherical to ellipsoid, colourless, 8 per ascus.
Notes: Hypogymnia is essentially a temperate genus of about 50 species worldwide. Twenty species occur in North America and 17 in B.C. The western Hypogymniae display a highly varied chemistry and spot tests are helpful in distinguishing between species. Note that what is usually referred to as a PD- medullary reaction in Hypogymnia may sometimes actually be discerned as PD+ pale yellow. In this case, however, the coloration is usually restricted to the upper portion of the medulla, while the lower portion remains white. By contrast, a “true” PD+ pale yellow reaction (e.g., as for H. rugosa) registers across the entire medulla, from top to bottom. Applying as little reagent as possible will help avoid ambiguity. Brodoa oroarctica was formerly treated within Hypogymnia.
Soredia absent AND
Upper surface pale brownish or more often whitish grey; lobules, if present, along margins; isidia absent; over bark and wood; variously distributed AND
Medullary ceiling predominantly white (or at least not distinctly dark: check toward thallus centre) AND
Lobes raised or at least not closely appressed, elongate; upper surface sometimes strongly convex at lobe tips; medulla PD+ yellow becoming bright orange; distribution various AND
Lobes distinctly pendent (except turned up at tips); upper surface whitish; lower surface often much expanded and clearly visible from above; essentially coastal
Cortex K+ yellow; medulla PD+ orange.
Atranorin, diffractaic, physodalic and protocetraric acids.
Source: Lichens of British Columbia