Usnea barbata (L.) Weber ex F.H. Wigg.

Nomenclatural data
Brit. Fl. 1: 206 (1780); emend. Jørgensen et al., Bot. J. Linn. Soc. 115: 280 (1994).—Usnea alpina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 214 (1936)—Usnea caucasica Vain., Természetr Füzetek 22: 275 (1899).—Usnea cembricola Motyka, Lich. Gen. Usnea Stud. Monogr. Pars. Syst. 1: 152 (1936).—Usnea freyi Motyka, Lich. Gen. Usnea Stud. Monogr. Pars. Syst. 1: 213 (1936).—Usnea implexa (Lam.) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 142 (1936)—Usnea maxima Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 154 (1936)—Usnea pendulina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 136 (1936)—Usnea plicata (L.) Weber ex F. H.Wigg.—Usnea prostrata Vain. ex Räsänen, Medd. Soc. Fauna Fl. Fenn. 46: 160 (1921).—Usnea rugulosa Vain.—Usnea scabrata Nyl., Flora 58: 103 (1875).—Usnea scrobiculata Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 144 (1936)—Usnea silvatica Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 151 (1936)—Usnea tenax Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 157 (1936)—Usnea tortuosa De Not., Giorn. Bot. Ital. 2, 1(1): 202 (1846).
Morphology
For a detailed description, see Halonen et al. (1998), Herrera-Campos et al. (1998), and Clerc (2007). The species is very polymorphic and may represent a collection of intergrading taxa; several characters (e.g. presence of fibrils, papillae, isidiomorphs; degree of depressions and ridges) vary greatly as seen also from the following synopsis. Thallus pendulous, may partly be divided into irregular segments by annular cracks; branches uneven in thickness, often with depressions and/or ridges; fibrils short, few to numerous; isidiomorphs few or absent [abundant in North America according to Brodo et al. (2001)]; papillae abundant, sparce or absent; soralia punctiform and irregular, few to abundant, develop on the top of eroded papillae, tubercles or ridges. Cortex thin; medulla thick and loose.
Medullary chemistry
Two chemotypes have been recorded: (1) with salazinic acid as a main substance (K+ yellow, orange or red, Pd+ yellow to orange) and protocetraric acid as an accessory substance; (2) without medullary substances (K–, Pd–) (Halonen et al. 1998).
In Estonia only the first chemotype is known (n=12) (Tõrra & Randlane 2007).
Remarks
Some specimens which have numerous fibrils may be confused with U. filipendula; consistence of medulla should be checked then (loose medulla in U. barbata, and dense in U. filipendula).
Click on images to see more!
Ecology and distribution
Europe (map legend)
Corticolous. Reported in Europe: Austria, Bulgaria, Czech Republic, Denmark, Estonia, Finland, Germany, Italy, Latvia, Lithuania, Norway, Poland, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine

Estonia
Grows mainly on conifers (on Picea 44% of examined specimens, on Pinus 22%), sometimes on Betula (17%) and rarely on other substrates (lignum, Alnus glutinosa) in coniferous or mixed forests, occasionally in wooded meadows. Very frequent in Estonia, found in all regions (Tõrra & Randlane 2007).