Thallus 5-15 (-30) cm, pendent or prostrate; branches to 0.5 (-0.8) mm diam., terete, becoming compressed towards the base and axils, branching irregularly isotomic-dichotomous, pale to dark brown, rarely blackish, the basal parts paler or concolorous with the apices. Fragmented black regions occasionally present, ± matt. Lateral spinules and pseudocyphellae absent. Soralia to 0.75 (-1.5) mm, abundant to scarce, rarely absent, tuberculate or fissure-like.
Anamorph: no information available.
Teleomorph: ascomata apothecia, very rare; disc 1-1.5 mm diam., brown to dark brown.
Chemistry: thallus Pd± red; medulla Pd–; soralia C–, K–, KC–, Pd+ red (fumarprotocetric acid).
Assessed by Woods & Coppins (2012) as of Least Concern.
The commonest species of the genus in the British Isles. Very variable, becoming contorted and spinulose in exposed situations, but generally easily recognizable by the tendency to have a pale base, fissure-like as well as tubercle-like soralia, the matt surface and smoky-brown colour. The soralia are always Pd+ red, but the thallus can be Pd+ or Pd–. Most often confused with Bryoria chalybeiformis, B. lanestris and B. subcana. B. fuscescens var. positiva (Gyeln.) Brodo & D. Hawksw. (1977) is no longer thought to be distinct.
Throughout the British Isles, common in hilly areas but decreasing. BLS map here.
On acid-barked trees, siliceous rocks, amongst mosses, on walls and worked timber.