Roccella tinctoria DC Taxon de Macaronésie.

     Thallus usually erect and tufted, to 5-15 cm high, potentially forming large colonies, branches more or less terete, branching dichotomous, notably towards apices, arising from a single holdfast, outer side brownish but inner whitish, surface more or less smooth and glossy on fresh samples, brown-greenish when moist, grey-brownish to brownish when dry; soralia abundant, farinose, flat to slightly convex. Cortex hyphae slightly interlaced, anticlinally arranged but not forming a conspicuous palisade plectenchyma;. Apothecia absent. Photobiont: Trentepohlia. Thallus: C-, K-, Pd-; soralia: C+ more or less bright red, K-, Pd-; epicortex layer: C+ pale red (suggesting pale red rings towards some soralia); medulla: C-, K-, Pd-. Saxicolous, belonging to the  Roccellatum canariensis Foll., thermophile and Macaronesian, on coastal rocks. N.B. Not to be confused with Roccella tuberculata with C- soralia and more greyish colours. N.B. This taxon is the sorediate form of Roccella canariensis but much more common than the latter. Was used as the main component of 'Orchilla' or 'Orseille' for dyeing tissues in red-purple.                

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.