Roccella tuberculata Vain.

    Thallus fruticose, shrubby, forming small stufts, pendulous or erect, composed of terete branches arising from a single holdfast, inner surface slightly yellowish, surface smooth, grey-brownish, brownish with grey-purple tinge when dry, brownish with green tinge when moist, with white, globose and farinose sorredia. Cortex hyphae slightly interlaced, anticlinally arranged but not forming a conspicuous palisade plectenchyma. Apothecia absent. Cortex: C-, K-, KC-, Pd-; subcortex : C+ red, K-; medulla: C-, K-, Pd-,; soralia : C-, K-. Saxicolous, on rocks or lava fields near the seashore in the Macaronesian islands. N.B. Always sterile, this taxon is chracterized by its negative chemical except for the subcortex.

Tehler A., Dahlkild A., Eldenäs P. & Feige G.B. 2004. The phylogeny and taxonomy of Macaronesian, European and Mediterranean Roccella (Roccellacea, Arthoniales). Acta Univ. Ups. Symb. Bot. Ups. 34:1, 405-428