Thallus to 3 cm tall, forming compact tufts, scattered or continuous in extensive patches; branches to 2 mm diam., chalk-white, pale greyish or ivory, ± erect, not or sparingly branched, cylindrical or somewhat flattened, longitudinally folded or furrowed, particularly towards the ± rooting base, smooth, rugose or scabrid-pruinose, solid; apices rounded, not markedly tapered. Soredia and isidia absent. Photobiont chlorococcoid.
Anamorph: not known.
Teleomorph: not known.
Chemistry: cortex C+ violet to yellow-brown (soon fading), K+ yellow to yellow-brown, KC+ yellow-orange to yellow-brown, Pd–; medulla UV± violet-glaucous or ± yellow (siphulin).
Assessed by Woods & Coppins (2012) as Near Threatened, due to its restricted distribution. It is listed under Section 2(4) of the Nature Conservation (Scotland) Act 2004.
A distinctive species unlikely to be confused with any other British lichen. Poorly developed material could be confused with Cladonia uncialis, which has a more yellow-green thallus composed of hollow podetia that are dichotomously branched with pointed apices and open axils. Thamnolia vermicularis differs in having pointed apices, hollow, extended branches, a prostrate habit and a different chemistry. Small, immature specimens have been mistaken for species of Pertusaria dactylina and/or Ochrolechia frigida.
Confined to NW Scotland, reported from around 8 sites in VC105 W Ross and VC108 W Sutherland. Locally frequent and possibly under-recorded.
On shallow peat or gravelly soil, often in shallow, temporary rain hollows in bedrock, or by pools in blanket bog, submontane or montane.