Flora of New Zealand Series

Thallus foliose, heteromerous, dorsiventral, lobate or ± squamulose, or ± areolate or ± granular, orbicular to spreading, loosely or closely attached, often with a prominent black or blue-black (rarely buff or pale) marginal prothallus of projecting, felted rhizines. Lobes variable, broad and rounded to laciniate, to microphylline and ± lobulate-squamulose. Upper surface dark bluish-green, plumbeous to fawnish or brownish-grey or olivaceous, smooth or wrinkled-plicate, matt, glossy or ± scabrid or pubescent, with or without soredia, isidia or phyllidia, margins entire to phyllidiate or sorediate or incised-crenulate. Medulla white. Photobiont blue-green, Nostoc. Lower surface tomentose or ± rhizinate, usually pale. Rhizines felted, silky, blue-black to whitish, often projecting beyond margins as a byssoid prothallus. Apothecia sessile to subpedicellate, rounded, biatorine, with a pale proper margin, lacking a thalline margin. Hymenium 100-120 µm, tall, colourless. Paraphyses numerous, compacted, simple, rarely slightly branched at apices c. 2 µm thick, slightly thickened apically. Asci clavate to subcylindrical, 8-spored. Ascospores uniseriate, simple, colourless, oblong to ellipsoid, often apiculate at one or both ends, epispore often indistinct or absent.

Parmeliella is a very heterogeneous assemblage of "oceanic" lichens more richly represented in the Southern Hemisphere than in the Northern Hemisphere. It is included in the Pannariaceae but at present it is poorly separated from other genera in this family having affinities with species in Pannaria, Leioderma, Degelia and Psoromidium and possibly also Psoroma. In most taxonomic accounts the absence of a thalline margin in the fruits alone distinguishes Parmeliella from Pannaria, but this character is scarcely a valid one for generic segregation [see Arvidsson and Galloway Lichenologist 13: 31-34 (1981)].

Some 50 species are described but it is likely that once Southern Hemisphere taxa in the Pannariaceae are better known a more rational view of generic limits will emerge with several species of Parmeliella consigned to other, redefined genera. Here Parmeliella in Müller Argovensis's sense is retained and 9 taxa are discussed, although several other undescribed species are known. The genus in New Zealand is still in need of systematic study and collection.

Species of Parmeliella colonise a variety of habitats from s.l. to 3000 m and may be corticolous, muscicolous or saxicolous. They prefer moist, humid habitats in moderate to deep shade. Seven of the described New Zealand species are endemic and two are of Australasian and Austral affinity. Jørgensen's [ Opera Bot. 45: 1-123 (1978)] account of European Pannariaceae gives the most detailed recent treatment of morphology, anatomy and nomenclature of Northern Hemisphere species of Parmeliella although he deliberately eschews discussion of generic limits pending examination of Southern Hemisphere populations.