Hypotrachyna exsecta
≡Parmelia exsecta Taylor, Lond. J. Bot. 6: 167 (1847).
Description : Thallus moderately to closely attached, 5–10 cm diam. Lobes often crowded, ±imbricate, sublinear, dichotomously to subirregularly branched, 1–3 mm wide. Margins entire to finely incised, rarely crenate, apices subtruncate to subrotund. Upper surface pale-grey to grey, glossy, smooth or wrinkled, emaculate, pustulate. Pustules subterminal, occasionally laminal, erumpent, eroding and becoming coarsely granular–sorediate and exposing black lower cortex. Medulla white. Lower surface black, glossy, with a naked brown, marginal zone, moderately to densely rhizinate. Rhizines dichotomously branched, often projecting beyond margins or growing horizontally from lobe margins. Apothecia rare, sessile to subpedicellate, 2–5 mm diam., disc concave, to undulate–distorted or fissured, pale-brown to brown, thalline exciple irregularly incised, ±pustulate.
Chemistry : Cortex K+ yellow; medulla K−, C+ orange, KC+ deep orange, Pd−; containing atranorin (minor), chloroatranorin (minor), barbatic acid (major), 4- O- demethylbarbatic acid (submajor), obtusatic acid (tr.), ±norobtusatic acid (tr.), ±diffractaic acid (tr.) and ±squamatic acid (tr.).
N: Northland (Helena Bay), South Auckland (Cuvier I., Kaimai Ra.) Kaiwaka, Raventhorpe. On brush of tree ferns, on ground among Pyrrosia eleagnifolia on humus between rocks, on Cordyline australis, in lowland, coastal forest. Known also from SE Asia, the Pacific, Australia and Papua New Guinea (Louwhoff & Elix 2002a: 52; McCarthy 2003c, 2006).
Western Pacific
Illustrations : Kurokawa (1986: 269, fig. 3 – as Parmelia exsecta); Louwhoff & Elix (2002a: 50, fig. 15).
Hypotrachyna exsecta is characterised by: the corticolous habit; the elevated, open dactyls that become erumpent, eroded and granular–sorediate with age; and barbatic acid and 4- O- demethylbarbatic acid (KC+ orange) in the medulla.
