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

General:
Common Name: The Rosette Lichens. Describes the centrifugal growth form characteristic of many of the species.
Small to occasionally medium stratified foliose lichens, corticate above and below, sorediate or isidiate or not, lobes closely appressed to loosely attached, elongate-linear to elongate, averaging to 0.5–2 (–3) mm wide, thin. Upper surface usually pale whitish grey, rarely darker, K+ yellow, white-pruinose or white-spotted, dull. Lower surface pale to blackish, dull, bearing scattered, short, simple rhizines. Medulla white. Photobiont green.
Apothecia located over upper surface, disc white-pruinose to black; spores 2-celled, ellipsoid, brown, 8 per ascus.
Over acid or especially calcium-rich substrates, including rock, soil, duff, bark and bone.
Notes: Thirty species of Physcia are reported for North America and 11 of these are known to occur in B.C. Physcia has been subdivided into several segregate genera, including Phaeophyscia and Physconia.

Species description:
Lobe margins bearing distinct cilia, the longest of these usually averaging to more than 1 mm long; lobe tips more or less raised AND
Lobe tips sorediate and/or apparently isidiate; ecology, distribution and status various AND
Lobe tips finely sorediate; marginal cilia numerous; over trees (rare over rock); widespread; frequent AND
Upper and lower surface of lobe tips separating, upper surface raised and hood-like when mature; soredia developing within the resulting cavity

Comments:
This species may sometimes intergrade withP. tenella.

Reactions:
Cortex K+ yellow.

Contents:
Atranorin.