Usnea flammea Stirt.

Nomenclatural data
Scott. Naturalist 6: 104 (1881).—Usnea dalmatica Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 263 (1936).—Usnea rupestris Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 323 (1937).
For a detailed description, see Clerc (1987b) and Purvis et al. (1992). Thallus shrubby, erect to subpendant, 3–8 cm; base pale, basal part often with distinct annular cracks; branches of even thickness, narrowing towards the apices, not swollen or inflated; fibrils present; papillae absent (especially in the basal area) or few, verrucous when present; soralia usually large, densely covered with isidiomorphs. Thickness and shining of the cortex varies; medulla dense to compact.
Medullary chemistry
Chemotype (1) with stictic acid as a main substance (K+ yellow to red, Pd+ orange) and lobaric, menegazziaic and norstictic acids as accessories.
Lobaric acid is present in ca 80% of the specimens tested; it can be used as a diagnostic character for this taxon as lobaric acid has not been recorded in any other European Usnea (Clerc & May 2007).
Belongs to the U. fragilescens aggregate.
Occurrence of distinct white annular cracks in the basal part helps to recognize the species.
Both cortex and inner structures (axis and medulla adjacent to the axis) may sometimes become orange due to decomposition of a medullary substance.
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Ecology and distribution
Europe (map legend)
Mainly corticolous (67%), may grow on mossy trees, shrubs, Calluna stems, decorticated wood etc., but also on rocks (33%) (Clerc 1987b). Its distribution is considered euoceanic, extending from the south-western coast of Norway and the British Isles to the Mediterranian region (Fos & Clerc 2000). Reported in Europe: Croatia, France, Greece, Great Britain, Ireland, Italy, Luxembourg (probably extinct), Norway, Portugal, Spain.