E-Flora BC: Electronic Atlas of the Flora of British Columbia

General:
Minute to small stratified foliose or occasionally fruticose lichens, corticate above and below, sorediate or isidiate or not, lobes closely appressed to loosely attached or semi-erect, short to more often elongate or elongatelinear, averaging to 0.3–1 (–2) mm wide, thin or somewhat thick. Upper surface orange or orangish, K+ purple. Lower surface pale, often whitish, often bearing scattered, short, simple rhizines. Medulla white. Photobiont green. Apothecia located over upper surface, disc orange; spores 2-celled, ellipsoid, colourless, 8 per ascus.

Over base-rich rock and bark, occasionally over bone.
Notes: Xanthoria is primarily a temperate genus consisting of approximately 15 species worldwide. Ten are reported for North America and six for B.C. The western Xanthoriae are in need of taxonomic revision; therefore the following account is tentative, pending further study. Chemistry is of little taxonomic value in this genus and is omitted.

Species description:
Soredia and isidia absent AND
Over rock; lobes closely to rather closely appressed to substrate (rarely semierect)

Comments:
The B.C. material is apparently heterogeneous.