Peltigera extenuata (Vain.) Lejka

   Foliose thallus formed of concave lobes 2-5 cm long and 1-2 cm wide, arranged in rosettes 5-8 cm in diameter, upper surface grayish, grayish-brownish in dry weather, dark green, brownish-olive green in wet weather, presence towards the margin of numerous soredia in discs 1-2 mm in diameter, finely granular, gray in youth then grayish-brownish; lower surface white, veined and covered with cottony rhizines frayed in ruffled brushes, hyaline white (hence its name in Canada of "Sheepish Pelt"). Apothecia very rare, in erect saddles. Ascospores hyaline, long fusiform, 40-60 x 3-4 µm. Photobiont: Nostoc. Cortex: K-, C-, KC-, P-; medulla and soralia: K-, C+ fleeting pink, KC+ fleeting pink, P-. A mountain, subarctic, and subalpine species that grows on stony soils.

_ Very closely related (and often confused!) with Peltigera didactyla, but the latter species is distinguished by its fleeting soredia that disappear after the apothecia appear, and its rarer, non-cottony rhizines.