Flora of New Zealand Series

Thallus foliose, heteromerous, lobate, dorsiventral, greenish-grey or whitish-grey to dark grey, sometimes with a whitish pruina, corticolous or saxicolous. Lobes closely attached, to ± ascending, irregularly or dichotomously branched. Upper surface plane or convex, white-maculate or emaculate, with or without soredia, upper cortex paraplectenchymatous or composed of hyphae ± parallel to the surface. Photobiont green, Trebouxia. Lower surface white to pale brown with whitish to dark brown rhizines. Apothecia laminal, lecanorine, sessile or subpedicellate, thalline exciple persistent, concolorous with thallus, disc dark brown to black sometimes with a white pruina, retrorse hairs absent or present at base of apothecia. Ascospores 8 per ascus, 2-celled, thick-walled, dark brown. Atranorin is a constant chemical constituent and often also zeorin.

Physcia is a large cosmopolitan genus of c. 50 species but occurring more commonly in the Northern Hemisphere. It is included in the family Physciaceae [Hafellener, Mayrhofer and Poelt Herzogia 5: 39-79 (1979)]. Of the 7 species known from New Zealand one appears endemic, the rest are cosmopolitan species frequently found on introduced trees in urban areas. The species are in need of revision in New Zealand. The following accounts [Thomson Beih. Nova Hedwigia 7: 1-172 (1963); Poelt Nova Hedwigia 9: 21-32 (1965); Ergebn. Forsch. Unternehmens Nepal Himal. 6: 57-100 (1974); Kashiwadani Ginkgoana 3: 1-77 (1975); Moberg Symb. bot. upsal. 22: 1-108 (1977)] contain much useful information.