Flora of New Zealand Series

Thallus crustose, continuous, rimose to areolate-cracked, thin or thick, granular or verrucose, occasionally subsquamulose especially at margins, white, greyish or yellowish, very rarely sorediate, corticolous and saxicolous. Photobiont green, Trebouxia. Apothecia lecideine, immersed to sessile, minute to large, rounded, disc black, strongly convex, occasionally roughened-scabrid or pruinose, margins thin, concolorous with disc, occasionally surrounded at base by a superficial thalline margin, often occluded. Hypothecium colourless or yellow-brown to red-brown or black and carbonaceous. Exciple continuous with or distinct from hypothecium, brown to black occasionally pale. Paraphyses thin, septate, simple or branched, brownish and slightly swollen at apices. Asci clavate, 8-spored. Ascospores greenish-brown to grey, 1-septate, without a hyaline epispore.

Buellia is a cosmopolitan genus of c. 400 species included in the family Physciaceae and closely related to Rinodina from which it is separated by the lack of a thalline margin to the apothecia. Useful accounts of the genus are those of Sheard [ Lichenologist 2: 225-262 (1964)] for British taxa, and Lamb [ Scient. Rep. Br. Antarct. Surv. 61: 1-129 (1968)] and Lindsay [ Br. Ant. Surv. Bull. 37: 81-89 (1973)] for Antarctic species.

Little systematic collecting of the genus has yet been undertaken in New Zealand and the species recorded are still very incompletely known. In the 19th century, 8 taxa were described from New Zealand collections by Stirton, Knight, Nylander, Müller Argoviensis and Hellbom and in the present century 10 new species were described for New Zealand by Zahlbruckner [ Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 371-376 (1941)] and Magnusson [ Sv. Bot. Tidskr. 37: 280 (1943)]. At least two cosmopolitan species occur in New Zealand. One lichenicolous species at present referred to Buellia [B. whakatipae Knight , T.N.Z.I. 8: (1876)] is probably more correctly placed elsewhere in Karschia [Hafellner Beih. Nova Hedwigia 62: 1-248 (1970)] or in a related non-lichenised fungal genus. The present account discusses 18 species, but is still introductory and incomplete.