Stereocaulon nanodes Tuck.

    Primary thallus persitent, composed of swollen phyllocladia (squamule-like structures specific to Stereocaulon), roughly granulose, more or less erect, lower surface sorediated, grey-greenish when moist, pale grey when dry; pseudopodetia scarce, short, 0.5-1 cm tall, more or less branched, with yellow-green globose soralia, sometimes with Stigonema-like granulose grey-bluish cephalodia. Apothecia very scarce. Thallus: C-, K+ pale yellow, KC+ purple (unconspicuous in the field), Pd+ yellow, UV+ whitish. Saxicolous, montane trends, on sheltered walls, more or less horizontal or flat slope siliceous rocks, enriched in metals (Fe, Mn, ...), notably in our prospection area on rocks of slag heaps of ancient slate quarries. N.B. In the field, rather similar to Trapelia glebulosa that grows in the same habitat but is C+ red. See also Stereocaulon pileatum with a distintive large apical soredia on pseudopodetium.