Flora of New Zealand Series

Thallus heteromerous, crustose to dwarf-fruticose, mainly grey but also white, yellow, green or blue-black, surface smooth, tuberculate, wrinkled-plicate and continuous, cracked or areolate. Cortex paraplecten-chymatous, becoming abraded or disorientated. Medulla white, variable in thickness, of loosely woven, thin-walled hyphae. Photobiont green, Trebouxia. Apothecia innate, within verrucae, generally elevated above thallus surface, single or several in pseudostromata; disc small and punctiform to broad and lecanorine. Parathecium weakly developed, never carbonised. Paraphysoids septate, branching from near base, variously spaced, becoming reticulately branched. Epithecium prominent, hyaline to dark, sometimes K+ violet. Hypothecium reduced, hyaline never K+ violet. Hymenium subglobose to discoid, hymenial gelatine colourless, yellow-brown or red. Asci clavate or cylindrical, 1-8-spored. Ascospores oval, ellipsoid, fusiform or cylindrical, simple, multinucleate, large, walls single or double, usually hyaline, mainly thick. Pycnidia immersed, globose or racemose, ostiolate or erumpent. Conidia cylindrical, filiform to acicular.

Pertusaria is a large genus of cosmopolitan lichens with c. 600 species [Dibben Milwaukee Pub. Mus. Publ. Biol. Geol. 5: 1-162 (1980)] included in the family Pertusariaceae. Species characteristically produce crustose thalli in which apothecial development takes place within thalline protruberances. These warts enlarge as the ascostromata develop and lead to the production of fruiting bodies immersed within fertile, elevated verrucae. Two kinds of ascocarp development are found, and together with spore-wall structure, appear good indicators of distinct subgenera. The poriform species of subgen. Pertusaria [Dibben, loc. cit.: 3] develop polycarpic fruits with double-walled spores and produce either ampliariate or pertusariate verrucae. The disciform species of subgen. Pionospora have monocarpic fruits with single-wall spores and produce either lecanorate or sorediate verrucae. Recognition of these types of verrucae is an essential prerequisite of species determination.

Ampliariate verrucae are conical in shape, have a reduced apical surface and no basal constriction, contain few apothecia, and release their spores through a single or small number of ostioles. Pertusariate verrucae are constricted basally, have a hemispherical or broadly flat-topped shape, contain many apothecia and release their spores through numerous ostioles that may be grouped inside disc-like depressions. Lecanorate verrucae resemble the solitary apothecia of Lecanora, rarely lack a supra-epithecial pruina, never develop as soralia and usually show no abortion of the hymenium or of its products. Sorediate verrucae resemble immature lecanorate verrucae, only initially may possess a supra-epithecial pruina, characteristically form strongly sorediate discs and show an advanced state of hymenial degradation with consequent loss of fertility [Dibben, loc. cit.: 3].

The most thorough account of anatomy, morphology, chemistry and taxonomy in the genus is that of Dibben ( loc. cit. ) dealing with species in North America.

Almost all species of Pertusaria in New Zealand are crustose, but P. dactylina, an alpine species, is ± subfruticose with well-developed clustered, dactyliform isidia. Crustose species are described from New Zealand material by Stirton [ J. Linn. Soc. Lond. Bot. 14: 464 (1875); Proc. phil. Soc. Glasg. 10: 296-297 (1877)]; Knight [ T.N.Z.I. 8: 313, 328 (1876); T.N.Z.I. 15: 349 (1883); T.N.Z.I. 16: 402 (1884)]; Krempelhuber [ Verhandl. zool.-bot. Ges. Wien 26: 451-452 (1876)]; Nylander, [ Flora 48: 338-339 (1865); J. Linn. Soc. Lond. Bot. 9: 253 (1866); Lich. N.Z.: 66-71 (1888)]; Müller Argoviensis [ Flora 67: 284, 286, 350, 462 (1884); Bull. Herb. Boissier 2, App. 1: 53-55 (1894); Bull. Soc. r. Bot. Belg. 31: 31 (1892)]; Hellbom [ K. Sv. Vet. Akad. Handl. 21 (3) 13: 73-77 (1896)]; Szatala [ Borbásia 1: 60 (1939)] and Zahlbruckner [ Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 329-338 (1941)]. The most recent account of the New Zealand species, that of Zahlbruckner ( loc. cit. ), is not based on a wide examination of type material but contains a key to many of the species recognised in New Zealand. The present account which is merely an appraisal of type specimens and in no sense a revision, discusses 23 species. Ten species are corticolous, 12 are found on rocks, and one is terricolous - muscicolous in alpine habitats.