Physcia jackii
=P. stellaris sensu Galloway (1985a: 394), auct. non (L.) Nyl.
Description : Thallus orbicular, rosette-forming to irregularly spreading (encircling twigs), closely attached from margins to centre, 1–2(–7) cm diam. Lobes plane to convex, 0.5–2(–3) mm wide, 3–5(–8) mm long, adjacent to loosely imbricate at apices, densely and complexly imbricate centrally, often also secondarily lobulate or hummocky centrally. Margins entire, shallowly notched, incised or scalloped, not noticeably thickened below. Upper surface pale greenish grey or blue-grey when moist, grey-white to creamish when dry, smooth to minutely granular–crystalline (×10 lens), occasionally minutely maculate centrally (×10 lens), epruinose, esorediate. Lower surface whitish at margins to pale-buff or creamish centrally, smooth, rhizinate. Rhizines sparse to frequent, simple to squarrose-branched (especially at apices), white to pale-tan, 0.4–1 mm long. Apothecia laminal, at centre of thallus, frequent, crowded–congested, sessile, constricted at base, rounded or contorted through mutual pressure, (0.2–)0.5–1(–2) mm diam., thalline exciple persistent, concolorous with thallus, entire, smooth to crenulate–striate, disc plane, matt, dark brown-black, with or without a fine, grey-white, delicately farinose pruina. Epithecium yellow-brown to chestnut-brown, 12.5–18 μm thick. Hymenium colourless, 100–112.5 μm tall. Hypothecium pale yellow-brown, opaque, of densely interwoven hyphae. Ascospores grey-brown, Physcia -type, (20–)22–25(–27.5) × 7.5–10 μm. Pycnidia sparse or absent, to numerous when present, immersed in thallus and visible as black dots. Conidia subcylindrical, 4–5 × 1 μm.
Chemistry : Cortex K+ yellow; medulla K− or + yellow; containing atranorin and zeorin
N: South Auckland (Thames, Coromandel Peninsula, Raglan, Hamilton), Taranaki (Waipapa, Mt Taranaki), Wellington (Rangitikei, Feilding). S: Nelson (Foxhill), Marlborough (Seddon, Hapuku River), Westland (Otira Gorge), Canterbury (Waikari, Banks Peninsula, Mt Somers, Peel Forest, Kelsey's Bush), Otago (Makarora, Glenorchy, Herbert, Broad Bay Otago Peninsula, Whare Flat, Akatore), Southland (Otautau, Queen's Park Invercargill, Awarua). St: (Traill Park, Butterfield's Beach Moturau Moana). On twigs and bark of trees and shrubs. Known also from Australia and South Africa (Moberg 2001, 2004b; McCarthy 2003c, 2006).
Western Pacific
Illustrations : Martin & Child (1972: 110. pl. 22 below – as Physcia stellaris); Malcolm & Galloway (1997: 135, 143 – as Physcia stellaris); Moberg (2001: 299, fig. 1).
Physcia jackii is characterised by: the corticolous habit; the neat, rosette-forming thallus; abundant, central apothecia; and the K−/K+ yellow medulla; a chemistry comprising atranorin (cortex) and zeorin (medulla). New Zealand material is very uniform chemically and also morphologically. The rather smooth, emaculate upper cortex and the crowded, central apothecia have led to the New Zealand material formerly being identified as P. stellaris. However, true P. stellaris lacks zeorin in the medulla, and no New Zealand collection formerly identified as P. stellaris has atranorin alone in acetone extracts.
