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

General:
Common Name: The Rag Lichens. Describes the whitish, often somewhat torn or tattered lobes of species.
Medium to large stratified foliose lichens, corticate above and below, sorediate or isidiate or not, lobes loosely appressed to semi-erect, elongate to short, often irregular, averaging to 3–20 mm wide, thin. Upper surface pale green to whitish or whitish blue, pseudocyphellate or not. Lower surface usually black toward thallus centre, shiny, bearing sparse, short, simple rhizines. Medulla white. Photobiont green.
Apothecia located on or near lobe margins, disc brown, often perforate; spores simple, ellipsoid, colourless, 8 per ascus.
Over trees and shrubs, occasionally over logs, rarely over rock.
Notes: Platismatia is primarily a temperate genus consisting of about 10 species. Of the six species reported for North America, five occur in B.C.

Species description:
Soredia present, occasionally intermixed with isidia AND
Pseudocyphellae absent over upper surface; soredia often intermixed with isidia; widespread; medulla C-

OR

Soredia absent; isidia present or absent AND
Upper surface whitish to very pale bluish or greenish, never yellowish (except specimens sometimes becoming yellowish in herbarium); lower surface often in part pale; pycnidia, if present, located entirely along lobe margins; apothecia generally absent; isidia present or absent AND
Lobes broader, averaging to 6–15 mm wide, short; upper surface smooth to strikingly ridged AND
Lobe margins more or less lacerate; upper surface smooth to occasionally broadly wrinkled; isidia, if present, irregularly scattered (i.e., not necessarily confined to ridges and/or lobe margins); widespread

Reactions:
Cortex K+ yellow.

Contents:
Atranorin and caperatic acid.