Taxonomy
The species was first species description, scientifically described by Carl Linnaeus in 1753. In his original description, published in ''Species Plantarum'', Linnaeus named it ''Lichen foliaceus'' and it as "a leafy, erect, compressed, branched, mealy lichen with warty sides". He provided several synonyms used by earlier botanists, including references to works by Dillenius (''Historia Muscorum'') and Vaillant (''Botanicon Parisiense''). In 1810, Erik Acharius formally transferred the species to the genus ''Ramalina'' in his work ''Lichenographia Universalis''. His detailed Latin description characterised the species as having an erect-compressed, glabrous (smooth), somewhat lacunose (pitted), sorediate, rigid, branched thallus with a whitish-greyish colouration and linear-attenuated branches. Acharius noted the apothecia as scattered, stalked, flat, slightly immarginate, and whitish, though he remarked they were very rare. He also carefully distinguished ''R. farinacea'' from similar species including ''Ramalina fastigiata, R. fastigiata'', ''Ramalina scopulorum, R. scopulorum'', and ''Ramalina pollinaria, R. pollinaria'', noting differences in soredia, thallus form, branch structure, rigidity, and apothecial characteristics. The botanical name, specific epithet ''farinacea'' derives from the Latin word (flour or meal), referring to the mealy or powdery appearance of the soredia that develop along the margins of the thallus branches. ''Ramalina farinacea'' belongs to a broader taxonomic group known as the "''Ramalina farinacea'' complex" that includes several closely related species distributed worldwide. The species boundaries within this species complex, complex have been subject to considerable confusion, particularly in tropical and subtropical regions. Throughout much of the 20th century, many tropical sorediate ''Ramalina'' specimens were misidentified as ''R. farinacea'', despite showing distinctive "nervulose" markings (longitudinal striations and pseudocyphellae) that differentiate them from the temperate species. Studies by Stevens (1983) clarified that these tropical specimens actually represent a separate but related complex comprising species such as ''R. pacifica'' and ''Ramaline nervulosa, R. nervulosa'' with their respective varieties. True ''R. farinacea'' is predominantly a temperate species, though it has been documented at higher elevations (above 600 m) in otherwise tropical regions such as Puerto Rico, Hawaii, and the Canary Islands. This taxonomic reassessment has helped define more accurate geographical and morphological boundaries for the species, though chemical variation within ''R. farinacea'' itself remains complex, with several distinct chemotypes recognised throughout its range.Description
''Ramalina farinacea'' typically grows 3–6 cm long, though it can reach up to 10 cm in some specimens. It forms tufted, hanging structures that originate from a clearly defined holdfast (biology), holdfast (attachment point). The lichen often divides into numerous flattened measuring up to 3 mm in width, which may occasionally appear slightly concave. Its colour ranges from yellow-green to dark grey-green. The surface of ''Ramalina farinacea'' is and smooth, with a firm texture. Internally, it possesses a solid medulla (lichenology), medulla (inner tissue layer) and a subcortex (supportive layer beneath the outer surface). A distinctive feature of this lichen is its numerous soralia—specialised structures for asexual reproduction—which are located along the margins of the branches. These soralia are discrete, circular to elliptical, saucer-shaped when young, and become flat with maturity. They produce fine, powdery soredia (reproductive propagules) measuring 20–30 μm in diameter that are pale yellow-green in colour. Sexual reproductive structures called apothecia are rarely observed and, when present, develop laterally on the branches. The (spores produced in sacs called ascus, asci) are broadly ellipsoidal and measure 8–15 by 5–7 μm. Chemically, ''Ramalina farinacea'' has four distinct chemotypes (chemical variants), all containing usnic acid in the medulla and soralia. These chemotypes can be distinguished by their chemical reactions: some show orange-brown or orange-red reactions with chemical tests (containing protocetraric acid), others display yellow-red or yellow-orange reactions (containing salazinic acid, sometimes with norstictic acid), some fluoresce blue-white under ultraviolet light (containing hypoprotocetraric acid), while others show no distinctive chemical reactions.Similar species
''Ramalina farinacea'' can be confused with several related species within the genus ''Ramalina'', particularly those in tropical and subtropical regions. The most similar tropical counterparts include ''Ramalina pacifica, R. pacific'' and ''Ramalina vervosa, R. nervulosa'' (with their respective varieties), which were historically misidentified as ''R. farinacea''. These tropical species can be distinguished by several key characteristics: ''Ramalina farinacea'' typically possesses a more loosely woven, arachnoid (spider web-like) medulla compared to the densely compacted medullary hyphae found in the tropical species. The branches of ''R. farinacea'' are generally less flattened and compressed than those of its tropical relatives. In subtropical regions, specimens of ''R. pacifica'' from New Zealand and Japan exhibit a smooth, bony-textured cortex that resembles ''R. farinacea'', but differ in their chemical composition. The distinctive "nervulose" markings—longitudinal striations and pseudocyphellae on the thallus surface—are often present in tropical species but less pronounced or absent in typical ''R. farinacea''. While the shape of soralia (reproductive structures) is similar across these species, their distribution and prominence on the thallus can vary. Chemically, ''R. farinacea'' contains usnic acid in the cortex and various medullary substances (protocetraric acid, salazinic acid, or occasionally no medullary substances), while the tropical species contain different combinations of depsides or depsidones, such as divaricatic and stenosporic acids (''R. nervulosa'') or salazinic acid (''R. pacifica)''. In field settings, ''R farinacea'' is primarily a temperate species, though it may appear at higher elevations in tropical regions. By contrast, species like ''R. pacifica'' and ''R. nervulosa'' predominantly occupy coastal tropical and subtropical habitats, particularly in mangrove ecosystems. ''Evernia prunastri'' may also superficially resemble shade forms of ''R. farinacea'', but the latter can be identified by its tough, cartilaginous subcortex and cylindrical structure with photobiont cells distributed beneath all surfaces.Habitat and distribution
''Ramalina farinacea'' occupies a diverse range of habitats and substrates. It commonly grows on trunks and twigs within shaded deciduous woodlands, but also thrives on sun-exposed, wind-swept isolated trees, hedgerows, and shrubland, scrub. The species can colonise wooden posts and is occasionally found free-living on sand dunes, though it very rarely occurs on rock surfaces. In North America, it is most abundant along coastal regions from approximately 30–60°N latitude, with several races extending inland. The species shows a strong preference for oceanic climates along both the Atlantic and Pacific coasts. In the United Kingdom, it is found throughout Britain, Ireland, and Wales. The morphology (biology), morphology of ''Ramalina farinacea'' shows distinct variation in response to environmental conditions. In air-polluted environments, specimens often develop as dark green, tufted forms with short, decumbent (lying flat), contorted or recurved branches. By contrast, in deeply shaded woodland settings, the lichen typically grows more elongated and pale in colour, with sparse, narrow branching patterns. These shade forms may superficially resemble ''Evernia prunastri'', but can be distinguished by their tough, cartilaginous subcortex (the layer beneath the outer surface) and their (cylindrical) structure with photobiont cells (the algal partner cells) distributed beneath all surfaces. Morphological features in this species are largely responses to microenvironmental conditions of substrate and climate rather than chemical composition. Research has shown that specific substrates or habitats often have characteristic branch widths and morphologies, with coastal localities typically having thinner-branched thalli than inland localities. Among ''Ramalina'' species, ''R. farinacea'' demonstrates exceptional tolerance to environmental pollutants. It is the least sensitive member of its genus to sulphur dioxide pollution (withstanding concentrations below 60 μg per cubic metre) and can also endure wind-blown inorganic fertilisers that might prove toxic to other lichen species. This environmental resilience contributes to its status as a common lichen throughout its range. The species shows distinct substrate preferences that vary by chemical race and geographic region. For example, in North America, the protocetraric acid race dominates populations on coastal and inland oaks (80–90%), while other chemical races compose major proportions of populations on alders in adjacent localities. Interestingly, a latitudinal gradient has been observed in the distribution of chemical races, with the hypoprotocetraric acid race becoming more frequent northward. While typically sterile, fertile specimens with apothecia do occur in some populations at rates ranging from zero to 14%. These fertile plants are usually found on tree trunks rather than on crown branches, and are typically large thalli in well-established populations from favourable, localized mesic habitats.References
{{Taxonbar, from=Q2129975 Ramalina, farinacea Lichen species Lichens described in 1753 Lichens of Europe Lichens of North America Taxa named by Carl Linnaeus