Flora of New Zealand Series

Parmelia mexicana Gyelnik, Feddes Repert. 29: 281 (1931).

Thallus foliose, loosely attached to 8 cm diam. Lobes variable, rather narrow (1-5 mm wide), weakly subdichotomously branching, branches discrete not imbricate, margins entire, sinuous, shining, black, slightly thickened, apices rounded or shallowly notched. Upper surface yellowish-green, shining, smooth at margins, wrinkled centrally, strongly isidiate, maculae and soredia absent. Isidia laminal not marginal, often dense and forming a ± areolate crust, delicate, rather friable, fine-granular at first, becoming coralloid-branched. Lower surface pale tan centrally, slightly darker brown at margins, shining, wrinkled- papillate. Rhizines rather short, sparse, simple, pale tan. Apothecia sessile, 2-8 mm diam., disc pale yellow to red-brown, shining, imperforate, margins entire, rather thin, often disappearing in mature fruits, thalline exciple smooth, shining, very occasionally sparsely isidiate. Chemistry: Cortex K-; medulla K+ yellow → red, C-, KC+ red, Pd+ orange. Salazinic and usnic acids.

N: Three Kings Is. S: Otago (Ahuriri Valley, West Matukituki Valley). On rock and on bark; coastal and subalpine. Rarely collected.

Cosmopolitan

X. mexicana is distinguished by its pale lower surface, coralloid-branched isidia and salazinic acid as the major medullary constituent. It is closely similar to X. scabrosa from which it differs in the morphology of the isidia and in its chemistry [Foo and Galloway Phytochemistry 18: 1977-1980 (1979)].