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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 bearing soredia and/or isidia (check lobe tips) AND
Soredia/isidia mostly confined to lower surface, especially at lobe tips; lobe tips upturned; lower surface pale, darkening only gradually toward thallus centre
Reactions:
All spot tests negative.
Contents:
No lichen substances reported.
Source: Lichens of British Columbia |
