Usnea glabrescens, Usnea glabrescens
Thallus 3-10(-15) cm tall,shrubby to subpendant, ± erect at the base, usually becoming ± pendulous towards the apices, main branches to 1.5 mm diam., cylindrical and not constricted at the point of attachment, often very richly branched and crowded towards the base, with long side branches, fibrils few or absent. Surface grey-green or yellow-grey, blackened at the base and usually with transverse and radial cracks, main branches with evenly spaced, densely papillate, thinner branches smooth. Soralia conspicuous, frequent, rounded, plane to slightly excavate, sometimes larger than half branch diameter, discrete or occasionally forming paler eroded patches, isidiomorphs absent or very rare. Cortex relatively thick, medulla dense to somewhat lax, axis generally thick.
Anamorph: not known.
Teleomorph: ascomata rarely produced.
Chemistry: three chemotypes occur: (a) thallus C–, K+ yellow→blood-red, KC–, Pd+ orange (usnic, norstictic and stictic acids); (b) C–, K+ yellow→blood-red (norstictic and salazinic acids); (c) thallus C–, K–, KC–, Pd+ yellow (usnic and psoromic acids).
Assessed as of Least Concern by Woods & Coppins (2012), but considered as Nationally Scarce.
This is a very elegant pendulous to subpendulous species, often densely tufted towards the base but with elongate, more or less hanging, little branched, flexuose extensions which extend noticeably beyond the main part of the thallus. Only soralia are present – isidia and isidiomorphs are never (or almost never) produced. The soralia are frequent, rounded, conspicuous (often pale yellow-green), well-shaped and barely excavate, never exceeding the width of the supporting branch. The base is markedly blackened and the medulla is very compact.
Differs from subpendulous morphs of U. subfloridana in the small, rounded, ± excavate soralia, always without isidia, as distinct from the abrasions left by shed isidia in U. subfloridana and also in chemistry. See also U. fulvoreagens. Many British reports of U. glabrescens probably refer to U. wasmuthii.
Rare and local. Throughout W British Isles and central Scotland.
On deciduous trees, in open, damp, humid situations, especially Salix carr.