Flora of New Zealand Series

Holotype: New Zealand. Taranaki, Mt Egmont [Mt Taranaki], c. 700 m, viii.1925, H.H. Allan 111 – UPS.

Description : Thallus small-squamulose in colonies 3–4 cm diam., consisting of partly ascending squamules, to 3 mm wide, with a greenish (brown when dry) upper surface, and a mainly glabrous, white lower surface with short hairs and a few dark rhizohyphae towards margins. Cephalodia grey-blue, marginal, bursting from below, totally dissolving in soredia that spread inwards on lobes. Apothecia common, to 2 mm diam., disc concave to flat, pale-brown; thalline margin squamulose. Ascospores narrowly ellipsoidal, apiculate at one or both ends, 25–30 × 10–15 μm, wall wrinkled.

Chemistry : TLC−, all reactions negative.

N: Known only from the type collection where it was found on pumice.

?Endemic

Illustration : Jørgensen (2004a: 250, fig. 13).

Psoroma cyanosorediatum is characterised by: the terricolous habit; the squamulose thallus of partly ascending squamules; marginal cephalodia that become sorediate; small apothecia, to 2 mm diam., with a flat, pale-brown disc; and narrowly ellipsoidal ascospores, apiculate at one or both ends, 25–30 × 10–15 μm, with a wrinkled wall. P. cyanosorediatum appears to be the sorediate counterpart of P. asperellum, though the soralia are formed in an unusual way. Apparently the hairs of the lower surface, as well as those below the apothecia, capture cyanobacteria as they do in P. hypnorum, the type species of the genus (Jørgensen 1978: 28–29). However, in P. cyanosorediatum the hairs dissolve into soredia, rather than forming cephalodia, somewhat reminiscent of those in Pannaria durietzii (q.v.), which are formed on the edges of well-defined cephalodia. P. cyanosorediatum is of course distinct from the foliose Pannaria durietzii, in being entirely squamulose, without radiating marginal lobes, and in not containing any secondary chemistry. P. circumsorediata appears to be the only presently known sorediate species in Psoroma (Jørgensen 2004a).