Flora of New Zealand Series

Thallus crustose, heteromerous, yellowish-, greenish- or whitish-grey, thin or rather thick c. 50-150 µm, surface smooth, wrinkled, verrucose-papillate or with isidia or soredia. Photobiont present in upper 60 µm of thallus, green, subspherical, 6-12 µm diam., Dictyochloropsis sp. Apothecia biatorine, sessile to subpedicellate, 0.5-5.0 mm diam., disc plane to convex, brown to black, sometimes with a greyish, beige or whitish pruina, margins yellowish, brown or black, usually paler than disc, sometimes darker, disc and margins usually slightly glossy. Epithecium c. 15 µm thick, usually diffusely orange-brown, sometimes with pigments or granular inclusions. Hymenium 80-260 µm tall, colourless, inspersed with oil droplets, c. 1-7 µm diam., I reaction variable. Paraphyses 1 µm thick, indistinctly septate, parallel, little branched, in epithecium more branched and anastomosing and slightly thickened (2-3 µm). Hypothecium usually 30-50 µm thick, usually less inspersed than hymenium. Ascospores 1-8 per ascus, colourless, 1-septate, to multiseptate, with thin septa, ellipsoid, ovoid or ± subspherical, straight or curved, sometimes with thickened apices, and a prominent, smooth or warted epispore. Chemistry: Zeorin and usnic acid or pannarin.

Megalospora is a mainly tropical genus of c. 26 corticolous species. It is included in the family Megalosporaceae [Hafellner and Bellemère Nova Hedwigia 35: 216 (1982)], though there are also affinities with genera in the Physciaceae and in Teloschistaceae. Main centres of speciation are New Zealand, New Guinea and Australia. Megalospora is monographed by Sipman [ Biblthca lich. 18: 93-169 (1983)] who records 7 taxa (6 species and 2 subspp.) from New Zealand. His treatment is adopted here. Four taxa are endemic and 3 have Australasian affinities.