Hypotrachyna sinuosa

Thallus 1–4 (–6) cm diam., rather compact, sometimes forming extensive patches; lobes (1–) 2–5 mm broad, separate or partly contiguous, overlapping centrally, dichotomously branched with wider, often ascending, truncate apices, axils markedly sinuate; upper surface yellow-grey to yellow-green, smooth, ± shiny, sorediate; soralia covering apices of ascending lobes, ± globose; soredia farinose; lower surface jet- black, rhizines dichotomously branched, numerous, often projecting beyond lobe margins. Apothecia and pycnidia not seen (in British material). Cortex K–; medulla C–, K+ yellow→red, KC+ red, Pd+ orange, UV– (usnic acid, salazinic acid [major] and traces of related compounds [including norstictic acid]). BLS 1017.

Readily separated from other Hypotrachyna species in the British Isles by the yellow-green thallus (usnic acid) and medulla K+ yellow→red (salazinic acid). Again, phylogenetic study has shown that this is not a monophyletic species in its traditional circumscription, and East African populations have been accommodated in a separate species, H. meridionalis (Kirika et al. 2019).