Flora of New Zealand Series

Type : Leiorreuma lyelii (Sm.) Staiger [=Opegrapha lyelii Sm.]

Description : Thallus crustose, brownish or olive greenish or creamish. Ascomata apothecia, lirellate, lirellae immersed to sessile, rounded, oval to irregularly flexuose, stellate or branched, with an open brown-black to grey-pruinose disc; margins prominent black, carbonised or lacking, sometimes breaking through hymenium and forming several, discrete, circular apothecia. Exciple entire, carbonised, continuous below with carbonised hypothecium. Hymenium 70–150 μm tall, I− or I+ blue to vinous. Epithecium brownish. Hamathecium of paraphyses, 1–2 μm thick, anastomosing, apices brownish. Asci 8-spored, Graphis -type. Ascospores brownish, thick-walled, I+ red or red-brown, transversely septate. Conidiomata pycnidia, immersed in thallus, ostiole brownish, minute, punctiform. Conidia short, bacillar, colourless, 3–4 × 1 μm. Chemistry −, or occasionally depsidones present.

Leiorreuma is a genus of c. 7 species included in the family Graphidaceae (Staiger 2002: 293–296). It is characterised by lirellae of variable shape, with a prominent thalline margin that sometimes breaks across the hymenium forming smaller, circular apothecia; a carbonised exciple that is continuous below the hymenium forming a thick, carbonised hypothecium; 8-spored, Graphis -type asci; and brownish, transversely septate, thick-walled ascospores. It occurs in both tropical and temperate biomes. One species is known from New Zealand.