General:
Medium to large stratified foliose lichens, corticate above and below, sorediate or not, lobes closely appressed, elongate, averaging to 0.3–0.5 mm wide, thin. Upper surface pale yellowish green, dull. Lower surface pale to black, apparently white-pruinose, bearing scattered, short, simple rhizines. Medulla white. Photobiont green. Apothecia located over upper surface, disc brown; spores simple, ellipsoid, colourless, 8 per ascus. Over acid rock in arctic-alpine to boreal localities.

Notes: Arctoparmelia consists of four species worldwide, all of which occur in B.C. For points of distinction with similar species in other genera, see the descriptions under Xanthoparmelia.

Species description:
Thallus lacking soredia AND Upper cortex firm, never eroding; lobe tips only rarely downturned AND Lower surface whitish or tan throughout; widespread

Reactions:
Cortex K+ pale yellow, KC+ yellow; medulla C+ slowly yellow, KC+ reddish.

Contents:
Alectoronic acid, atranorin and usnic acid.

Source:  Lichens of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration By:  Trevor Goward

Synonyms and Alternate Names:
Arctoparmelia aleuritica (Nyl.) Hale
Parmelia aleuritica Nyl.
Parmelia centrifuga
Xanthoparmelia centrifuga (L.) Hale