Usnea ceratina Ach.

Nomenclatural data
Lichenogr. Univ.: 610 (1810)
Morphology
For a detailed description, see Halonen et al. (1998), Herrera-Campos et al. (1998) and Clerc (2007). Thallus shrubby to pendulous, coarse and tough; fibrils and papillae sparse to numerous; tubercles conspicuous and numerous on larger branches, becoming white at the top and bearing soralia and/or isidiomorphs. Cortex thick and glossy; medulla thick and dense, light pink to pink, occasionally white; central axis pink to almost red, rarely white.
Medullary chemistry
Diffractaic acid (K–, Pd–, C+ pale yellow, CK+ yellow to yellow-orange) is present as a main substance, barbatic and squamatic acids as accessory substances; amount of unidentified pink and/or yellow pigments varies.
Remarks
Distinguished by the coarse-texured thallus and unique chemistry (presence of diffractaic acid); pink medulla and axis are of help in determination of juvenile specimens (James 2003).
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Ecology and distribution
Europe (map legend)
Corticolous, on old trees with a rather acid bark in well-lit situations (Purvis et al. 1992, Diederich et al. 2008). The species is widely distributed both in the northern and southern hemispheres; reported in Europe: Austria, Belgium, Bulgaria, Czech Republic (probably extinct), Northern France, Germany, Great Britain, Hungary, Italy, Ireland, Latvia, Luxembourg (probably extinct), Netherlands (probably extinct), Poland, Portugal, Romania, Slovakia (probably extinct), Slovenia, Spain, Sweden (probably extinct), Switzerland, Ukraine.

Estonia
Not known in Estonia or Lithuania but reported from north-eastern Latvia, Donikava, on conifers (Piterāns 1982, 2001). Occurrence in southern Estonia can be presumed (Tõrra & Randlane 2007).