Roccella fuciformis (L.) DC
Thallus shrubby, most often pendulous, up to 10-15 cm long, made of branches, flattened, strap-shaped, sometimes scythe blade-shaped, pale grey, pale lilac, brown-lilac, lilac or lilac-purple tinged, medulla white in section. Branches are partially covered with soralia, more or less circular, forming small white flattened mounds clustered towards the margins. This species is seldom fertile except during the last years in Brittany. Apothecia marginal or laminal, scattered over the branches, more or less cup-shaped, 1-2 mm diam., emerging through the cortex and visible as small black protruding buds edged by a membrane concolourous to the thallus . Ascospores colourless, fusiform, straight or slightly curved (banana-shaped) 3-septate, 25-30 x 5-7 µm. Ccortex with palisade plectenchyma, K+ pale yellow, vanishing, C- (see Roccella fuciformis forma, cortex C+ red-orange, on rocks exposed to the South-West), soralia: C+ pink to red. Photobiont: Trentepohlia. Rather common, forming colonies under overhangs or on dry vertical walls of large rocks on the foreshore exposed to North or East, but this thermophilic species is frost sensitive. Sometimes found together with Roccella phycopsis of which the branches are not strap-shaped and far less frequent in our prospection area. N.B. Tinctorial species propitious to preparation of purple dyes. Very close to Roccella maderensis that is more thermophiles, paler grey-brownish and cortex C+ red.
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.