Flora of New Zealand Series

Holotype: New Zealand. South I., Canterbury, Nina Valley, on Nothofagus by bog, 11.ix.1981, P.M. Jørgensen s.n. – BG. Isotypes – BM, CHR.

Description : Thallus squamulose, forming extensive patches, sometimes distinctly pulvinate, up to 5 cm diam., surface emerald-green when wet, buff-brown when dry. Squamules incised, elongate, narrow, to 1 mm diam., loosely attached or subascendent. Cephalodia squamulose, similar in structure to thalline squamules, bright-blue when wet, brownish when dry and not readily distinguished from thalline squamules, containing Nostoc, cells 4–6 μm diam. Apothecia rare, only in green parts of thallus, sessile, to 3 mm diam., disc plane, brown, epruinose, without sterile plugs or ridges, thalline margin distinctly crenulate, persistent, raised, concolorous with thallus or occasionally incorporating Nostoc. Hymenium 90–120 μm tall, brownish in upper parts otherwise hyaline, I+ deep-blue. Asci subclavate, 60–90 × 11–18 μm, with weakly developed apical, amyloid ring structure. Ascospores ellipsoidal, 12–16 × 7–10 μm, with rugulose perispore to 1.5 μm thick, apices occasionally tapering. Pycnidia not seen.

Chemistry : TLC−, all reactions negative.

N: Wellington (Lake Rotoaira, Whakapapanui Stream). S: Nelson (Travers Valley), Canterbury (Nina Valley). St: (Port Pegasus, Small Craft Retreat, the "Enchanted Forest"). On bark of Dacrydium cupressinum and Nothofagus solandri var. cliffortioides in montane rainforest, 500–1150 m, s.l. on Stewart I. Known also from New South Wales (Jørgensen & Wedin 1999: 346; McCarthy 2003c, 2006).

Australasian

Illustrations : Jørgensen & Wedin (1999: 342, fig. 1; 345, fig. 3).

Psoroma geminatum is characterised by: the corticolous habit; blue-green squamules among green thalline squamules (hence the specific epithet – geminatum = twinned) or in separate parts of thallus. The cyanobacterial squamules are darker and narrower (sometimes nearly linear, cylindrical and articulate-knobbly) than the green squamules, and they are very brittle, acting as vegetative diaspores. The cepahlodia resemble Pannaria crenulata, but differences in chemistry in this species (vicanicin and traces of argopsin) distinguish this latter species.