Thallus 2-8(-20) cm tall, at first erect, ± tufted, sometimes ± becoming pendulous. Main branches to 1.5 mm diam., cylindrical, not inflated, branching irregular, isotomic-dichotomous with numerous laterals of unequal length. Surface pale to dark grey-green, usually conspicuously blackened at the base, with minute transverse cracking and sometimes interconnecting longitudinal cracks creating a brickwork-like pattern. Main branches often densely papillose especially towards the base, occasionally with white, rounded or oval abraded areas, terminal parts and fibrils smooth with scattered papillae. Soralia slightly excavate, discrete to confluent, ulcer-like and longitudinally stretched (at least when mature). Secondarily ± corticate isidiomorphs rare and present only on young thalli. Medulla dense.