Usnea subscabrosa Motyka

Nomenclatural data
Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 313 (1937).
For a detailed description, see Clerc (1992, 2007) and Herrera-Campos et al. (1998). Thallus erect, subpendant to pendant, up to 25 cm long, stiff; base pale or red-brown pigmented; branches even in thickness, slendering evenly towards the apices, not constricted at the point of attachment; fibrils usually absent, occassionally scarce, rarely numerous; papillae absent or present, verrucous; soralia present, punctiform to somewhat enlarged (less than half width of the branch bearing them), mainly on small branches and the apices; isidiomorphs absent to abundant (on young soralia). Cortex very thick (9–17%), characteristically shiny; medulla thin, compact.
Medullary chemistry
Chemotype (1) with protocetraric acid (K–, Pd+ orange) as a main substance and fumarprotocetraric and barbatic acids as accessories (Herrera-Campos et al. 1998); chemotype (2) with tamnolic acid as a main substance (K+ yellow to slowly red, P+ orange) and squamatic acid as an accessory has been reported from Azores (Clerc 2006).
Morphologically very variable species (the characters which vary in a large scale: growth habit from shrubby to pendulous, presence and abundance of fibrils, papillae and isidiomorphs, shape of soralia); important diagnostic characters include very thick and vitreous cortex, and protocetraric acid as a main medullary substance.
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Ecology and distribution
Europe (map legend)
Both corticolous and saxicolous; moderately acidophilous, anitrophilous and toxitolerant (Fos & Clerc 2000). Distributed in south-western areas of Europe. Reported in Europe: Great Britain, Italy, Portugal, Spain.