Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Life habit: lichenized Thallus: fruticose, pendent, sparsely dichotomously branched, main and terminal branches flattened or terete, branches 2-5 -(10) mm thick and usually 5-15 cm long lobe surface: creamy white-grayish to grayish-brown, smooth or wrinkled, sparsely pruinose or epruinose; soredia (often in soralia) present or absent, isidia absent cortex: hyphae anticlinally arranged, 40-70 µm thick medulla: loose above, byssoid or chalky; below plectenchymatous in area of the basal plate (holdfast) and often (yellowish) brown photobionts: primary one a Trentepohlia, seconddary photobiont absent attachment: by holdfasts, including an hypomedulla which is usually brown to dark brown (sometimes with a yellowish tinge) Ascomata: apothecioid, lateral, circular in outline, immersed or sessile with constricted base, up to 2.5 mm diam.; disc: exposed, white with a rimose, pruinose layer; exciple: initially with algae and a cortex, later the algae often displaced and the cortex eroded; proper exciple: a thin parathecium, sometimes inconspicuous; epithecium: 40-50 µm, brown, with paraphysoids intertwined, sparsely branched; hymenium: 70-90 µm high; paraphysoids: sparsely branched, hyaline, 1-2 µm diam.; hypothecium: distinct, dark brown (carbonaceous), not extending down into medulla asci: clavate, 60-85 x 12-14 µm ascospores: fusiform, curved, smooth, 3-septate, hyaline Conidiomata: pycnidial, solitary, immersed, black, 0.1 mm diam. conidia: filiform, curved, 16-21 x <1 µm Secondary metabolites: orcinol and beta-orcinol depsides, aliphatic acids Geography: a pantropical genus and extending into adjacent temperate regions, especially those with Mediterranean climates Substrate: on bark or rock. Notes: In the checklist of North American lichens Esslinger and Egan (1995) list as many as nine species of Roccella, all of which have been reported from California (Darbishire 1898; Hasse 1913; Tuckerman 1882). Some of the names such as Roccella fuciformis, R. phycopsis and R. tinctoria are European species, that have been incorrectly reported from North America. The other species, Roccella babingtonii, R. decipiens, R. difficilis, R. fimbriata, R. montagnei and R. peruensis, are all part of a difficult species complex with a distribution that extends down to mediterranean Chile in South America and include adjacent islands such as the Galapagos and with an offshoot into the Caribbean region. They may even have a global distribution. This treatment agrees with Hale and Cole (1988) that only two taxa from that species complex should be recognized from California, although different names are used here. A third taxon, R. portentosa, is reported from southern Baja California Sur.