Flora of New Zealand Series

Description : Thallus forming extensive, flat, radiating rosettes on rocks, to 8 cm diam.; centrally dissolving into a crust of bluish lobules, to 2 mm wide, initially developing on upturned lobe margins; peripheral lobes radiating, elongate, to 3 mm wide; 250–300 μm thick. Photobiont Nostoc, in clusters. Upper surface smooth, glossy, blue-black when wet, pale-brownish when dry. Lower surface with some marginal, blue-black rhizohyphae. Apothecia rare, dispersed among central lobules, to 1 mm diam., disc brown, with central plugs of sterile tissue, thalline margin crenulate. Hymenium I+ dark-blue. Ascospores ellipsoidal, immature.

Chemistry : TLC−, all reactions negative.

S: Nelson (Long Lake, Tasman Mts). On damp rock faces. Known also from Lord Howe I., New South Wales and Tasmania (Jørgensen 2001b: 113).

Australasian

Illustration : Jørgensen (2001b: 114, fig. 1).

Pannaria centrifuga is characterised by: the saxicolous habit; the radiating peripheral lobes and the bluish marginal lobules best developed on central lobes, the lobules are often numerous, especially in large, rosette-forming thalli, which disintegrate centrally as the thallus grows. It appears to be the non-sorediate counterpart of P. elixii, but is distinguished from it by the appressed thallus, the smooth, epruinose and often glossy upper surface, the absence of soredia and the negative lichen chemistry. It is related to P. delicata (q.v.), which also has no chemistry, and apothecial characters are similar, this latter species however, grows upwards and dies internally in contrast to the peripheral renewal of thalli of P. centrifuga (P.M. Jørgensen, pers. comm.).