Flora of New Zealand Series

Thallus foliose, lobate, dorsiventral, heteromerous, loosely to closely attached, ± rosette-forming to ribbon-like, corticolous, saxicolous or terricolous. Lobes linear or linear-cuneate to spathulate, branching ± dichotomous to irregular. Upper surface greyish to grey-white, or greenish-white, with or without pruina, with or without soralia, with or without squamules, rarely isidiate. Medulla white. Photobiont green, Trebouxia. Lower surface corticate or ecorticate, white, pale to dark greyish or often coloured with pigments, yellow-orange (K+ purple). Rhizines arising from lower-surface, white to black, simple to densely branched. Apothecia lecanorine, with a well-developed thalline exciple, disc brown or brown-black, epruinose, margins sometimes sorediate. Ascospores thick-walled, surface smooth, 1-septate, with or without sporoblastidia, dark brown.

Heterodermia is a cosmopolitan genus of c. 40 species included in the family Physciaceae and best developed in temperate areas [Poelt Nova Hedwigia 9: 21-32 (1965); Kurokawa Beih. Nova Hedwigia 6: 1-115 (1962); J. Hattori bot. Lab. 37: 563-607 (1973); Swinscow and Krog Lichenologist 8: 103-138 (1976)]. In New Zealand 7 species are found, mainly on coastal rocks or soils or on introduced trees in urban areas, being most common in North I. H. leucomelos is widely distributed on native vegetation, H. podocarpa rarely found. Morphology, anatomy and chemistry in the genus is discussed by Swinscow and Krog ( loc. cit. ).