Usnea articulata (All Fungi)
Thallus to 1 m or more long in favoured sites, pendent or scrambling, main branches to 3 mm diam., the older portions strongly inflated, ± cylindrical, forming sausage-like segments. Young or terminal branches less inflated, adjacent segments interconnected by a cartilaginous axil or with annulations, sparingly branched at base, more richly irregularly branched towards apices, with few, ± flexuose lateral branches, often in a loose, flexuose tassel. Base brown or concolorous with the main thallus branches. Cortex thin (5-7% of diam.), surface pale to mid green-grey, uniformly smooth or rarely, in part, minutely roughened-papillate, with scattered, slightly raised white, dot-like, comma-like or irregular linear pseudocyphellae. Medulla wide, lax, cottony-arachnoid, especially in inflated parts. On some (often narrower) branches the pseudocyphellae convert into soralia or isidia, the latter sometimes having pigmented apices.
Anamorph: unknown.
Teleomorph: ascomata unknown in Britain.
Chemistry: Medulla C–, K–, KC–, Pd+ red (fumarprotocetraric and usnic acids).
In GB&I, classified as Near Threatened, a BAP Priority Species and a species of International Responsibility, due to the decline in its distribution since 1960. It is listed in Section 41 (for England) and 42 (for Wales) of the NERC Act (2006). See Anon. (2010) and Woods & Coppins (2012).
Usually easily identified by the prostrate to untidily hanging, inflated, sausage-like older parts of the thallus. There is little surface ornamentation apart from a few, white, comma-like pseudocyphellae, and soralia and isidia are mostly absent.
Young specimens, which lack the characteristic articulations, could be confused with U. flammea which is more erect, has a bottle-brush appearance and a K+ yellow-red medulla (stictic acid complex).
In GB&I, S & SW England, Wales, north to Isle of Man, Ireland, formerly extending to N England.
In well-lit, xeric situations, especially on inclined branches in crowns of trees, rarely scrambling over low vegetation, also on the ground in a few coastal sites; locally abundant. One of the most sensitive species to SO2 air pollution.