Xanthoparmelia dichotoma
≡Parmelia dichotoma Müll.Arg., Flora 69: 257 (1886).
Description : Thallus loosely adnate on rock, 7–10 cm diam. Lobes loosely imbricate, linear-elongate, dichotomously branching, 15 mm long and 1–2 mm wide, apices subascendent, exposing lower surface. Upper surface pale yellow-green to grey-green, glossy, emaculate, smooth, without isidia or soredia, margins glossy, black or brown. Lower surface glossy to matt, black to rarely brownish, sometimes paler towards apices, rhizinate. Rhizines very sparse, simple, robust, concolorous with lower surface. Apothecia rare, subpedicellate, to 6 mm diam., disc concave to plane, glossy, brown; thalline exciple smooth, glossy, thick, entire or crenulate. Ascospores 5–8 × 3.5–5 μm. Pycnidia rare. Conidia not seen.
Chemistry : Cortex K−; medulla K−, C−, KC+ rose-pink, Pd−; containing usnic acid, loxodin and norlobaridone.
N: Northland (Three Kings Is) to South Auckland. On coastal rocks. Known also from southern Australia and Tasmania (Elix 1994s: 233; McCarthy 2003c, 2006).
Australasian
Illustrations : Galloway (1981a: 535, fig. 5B); Hale (1990: 102, fig. 36A); Elix (1994s: 231, fig. 95C).
Xanthoparmelia dichotoma is characterised by: the saxicolous habit; the narrow, markedly linear-elongate lobes that are dichotomously branched; the black to brown-black, wrinkled lower surface with very sparse, robust rhizines; and loxodin and norlobaridone in the medulla.
