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Common Name: The Mouse Lichens. Reflects the resemblance of the species to “mouse” lichens of the genus Pannaria.
Small to medium stratified squamulose lichens (ours), corticate above and below, nonsorediate, nonisidiate, cephalodia external, squamules closely to rather loosely appressed, averaging to 0.2–0.5 mm wide (in BC). Upper surface usually brownish, smooth. Lower surface pale and resting on a pale hypothallus, lacking rhizines. Medulla white. Photobiont green, except with secondary blue-green cephalodia.
Apothecia located over upper surface, disc reddish brown; spores simple, ellipsoid to spherical, colourless, 8 per ascus.
Over rock, soil and trees.
Notes: Psoroma, with approximately 35 species worldwide, is primarily a temperate genus of the southern hemisphere. Two species are reported for North America and only one of these occurs in B.C. A second species is not conclusively identified. Psoroma is closely related to Pannaria, but contains a green algal photobiont. The taxonomic distinctness of these two genera is in question.
Upper surface orangish brown; hypothallus pale; apothecia frequent; widespread
Cephalodia are occasionally present in this species. These are similar in form to the lobes, but are dark and contain a blue-green cyanobacterium.
All spot tests negative, except hymenium I+ strong blue.
No lichen substances reported.
Source: Lichens of British Columbia