General: Common Name: The Frost Lichens. Alludes to the characteristic presence of white pruina over the upper surface of the species. Medium stratified foliose lichens, corticate above and below (ours), sorediate or isidiate or not, lobes appressed to loosely attached, elongate, averaging to 0.5–2 (–3) mm wide, thin. Upper surface brownish, except often heavily white-pruinose, K-, dull to somewhat shiny. Lower surface pale to more often blackish, dull, bearing numerous squarrose rhizines. Medulla white or occasionally pale yellow. Photobiont green. Apothecia located over upper surface, disc white-pruinose; spores 2-celled, ellipsoid, brown, 8 per ascus. Over calcium-rich substrates, including rock, soil, duff, bark and bone. Notes: Seven species of Physconia are reported for North America and five of these are known to occur in B.C. Chemistry is of little taxonomic importance in this genus, with the exception of the K+ yellow medullary reaction of P. enteroxantha. See, however, the notes under that species. The species currently assigned to Physconia were formerly treated within Physcia. The genus is under taxonomic review by T. Esslinger; this treatment is provisional.
Species description: Thallus lacking soredia and isidia AND Over soil, duff or mosses (rare also over bark at bases of shrubs); lobe tips often somewhat upturned; apothecia rare; common
If more than one illustration is
available for a species (e.g., separate illustrations were provided for two
subspecies) then links to the separate images will be provided below.
Note that individual subspecies or varietal illustrations are not always available.
