Peltigera didactyla (With.) J. R. Laundon

    Thallus foliose, often limited (notably at first) to a few ear-shaped lobes, more or less immersed in the ground, sometimes, when mature, forming rosettes, 3-5 cmm diam., margin upturned, finely tomentose; upper surface grey, grey-brownish, brownish to green olive, young specimen more or less covered with laminal soralia, greyish, dull grey-yellowish, soralia vanishing at maturity with apothecia development; lower surface whitish, prominent veins, rhizine simple, brownish, seldom brush-shaped. Apothecia located towards lobe margins, isolated or in small clusters (2-4), erect and finger-shaped in old specimen, exciple indented or crenulate, brown-reddish then brown-chesnut. Ascopores narrowly elongate, acicular, 3-7-septate, 40-75 x 3,5-4,5 µm. Photobionte : Nostoc. Thallus and soralia chemical spot tests negative. Typical of wastelands and badlands, paths and tracks shoulders, waste heaps and quarries, etc.

_ This species is polyphyletic and contains several taxa including Peltigera extenuata (Vain.) Lojka, mountainous, very rarely fertile, whose soralia are persistent: C+ fleeting red, KC+ fleeting red, the underside of which is covered with white cottony rhizines (like a "sheepish pelt").

N.B. When adult, and devoid of soralia, easily mistaken with Peltigera rufescens and  Peltigera membranacea that may be found in the same habitat.