Cladonia arbuscula  

Thallus: primary thallus crustose, evanescent. Podetia 40-100 mm tall, yellow-green to yellowish grey, paler at the bases which frequently become necrotic; main axis distinct, often robust, 1.1.5 mm diam.; surface ± uneven-roughened, ecorticate but only inconspicuously felty, the algae held in small, hardly protruding and often elongate areoles, soredia absent; fairly richly to richly branched, terminal branches notably recurved and markedly orientated in one direction, branching predominantly trichotomous or tetrachotomous at apices; young apices <2 mm diam., blunt.
Anamorph: conidiomata pycnidia, frequent, ± cylindrical to ovoid, the contents colourless.
Teleomorph: ascomata apothecia, rather rare, when present in clusters at branch tips, 0.5-1mm diam., ± spherical, brown, inconspicuous.
Chemistry: thallus C–, K–, KC+ yellow, Pd+ rust-red, rarely yellow, UV– (psoromic or fumarprotocetraric and usnic acids).

In GB&I, Cladonia arbuscula has been separated into subspp. arbuscula and squarrosa; the latter was considered to be more common and the dominant European subspecies, and was separated from subsp. arbuscula primarily by a Pd+ rust-red rather than yellow reaction. Recent molecular data suggests that the distinction between the two subspecies is blurred, and they are not separated in this account.