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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 distinctly dark almost throughout AND
Upper surface distinctly and strongly convex throughout (including near lobe tips), also often swollen; basally constricted marginal lobules present or absent AND
Lobes appressed or pendulous; lobe tips mostly hemispherical, perforate or not; variously distributed AND
Basally constricted marginal lobules more or less abundant; medulla PD or PD+ yellow becoming bright orange AND
Lobes averaging to 1.5–2.5 (–3.5) mm across, never knobby; medulla PD-; mostly inland
Cortex K+ yellow; medulla KC+ red.
Atranorin and physodic acid.
Source: Lichens of British Columbia