Punctelia borreri (Sm.) Krog
Lichen borreri Sm. in Sm. et Sowerby, Engl. Bot. 25: 1780 (1807).
Thallus orbicular, closely attached, to 10 cm diam., corticolous rarely saxicolous. Lobes broad (4-10 mm wide), rounded, somewhat dissected, often crowded, margins entire, sinuous. Upper surface greenish-grey to pale mineral grey, margins tinged brownish or sometimes white-pruinose, shining, smooth, wrinkled centrally, pseudocyphellae small, punctiform, most obvious at margins, becoming sorediate centrally. Soralia derived from pseudocyphellae, clustered at centre, sometimes marginal, punctiform to confluent, soredia fine, dusty, white to grey-white. Lower surface black, rhizinate. Rhizines simple, black or pale brown, numerous, to margins. Apothecia rare, subpedicellate, to 8 mm diam., disc brown, matt, plane, imperforate, margins entire, pseudocyphellate and becoming sorediate, thalline exciple pseudocyphellate. Ascospores broadly ellipsoid, 15-18 × 12-15 µm. Chemistry: Cortex K+ yellow; medulla K-, C+ rose pink, KC+ rose pink, Pd-. Gyrophoric acid and atranorin.
N: Rotorua southwards. S: Greymouth, and several coastal localities in Otago from Trotters Gorge to Akatore. Mainly lowland or coastal from bark or lignum, rarely from rock. Rather seldom collected.
Cosmopolitan
P. borreri is characterised by its black lower surface, pseudocyphellae which become sorediate and by gyrophoric acid in the medulla. It is distinguished from P. subrudecta which has a pale lower surface and lecanoric acid as the main medullary constituent.
