Usnea cavernosa Tuck.

Nomenclatural data
In Agassiz, Lake Superior, p. 171 (1850).
For a detailed description, see Halonen et al. (1998), Herrera-Campos et al. (1998), and Clerc (2007). Thallus pendulous, with parallel branches; base pale; branches uneven in thickness, conspicuously foveolate and ridged, annular cracks may be numerous but generally are inconspicuous; fibrils absent to scarce; papillae absent; soralia and isidiomorphs absent. Cortex thin, shiny; medulla loose to dense, thick; central axis often sinuous.
Medullary chemistry
Chemotype (1) with salazinic acid as a main substance (K+ red, Pd+ yellow to orange) is known from Europe, North America and Asia; chemotype (2) with no medullary compounds (K–, Pd–) is reported as very rare in British Columbia (Halonen et al. 1998).
Pendulous thallus with parallel foveolate branches, and absence of papillae, soralia and isidiomorphs are the diagnostic characters of this easily distinguished species.
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Ecology and distribution

Europe (map legend)
Corticolous, mainly on conifers (Halonen et al. 1998). Reported in Europe: Austria, Bulgaria, Germany, Italy, Poland, Romania, Slovakia (probably extinct), Slovenia, Switzerland, Ukraine.