Flora of New Zealand Series

Holotype: New Zealand. Campbell I., SW slope of Mt Honey, c. 487 m, 31.xii.1969, R.C. Harris 4895B, MSC 130628.

Description : Thallus closely attached, irregularly spreading over rock, 1–2(–3) cm diam., margins entire, somewhat swollen, not flat, in places breaking up into small, separate, flattened squamules, without a marginal prothallus. Upper surface pale greenish grey, here and there suffused ochre or rusty, continuous to irregularly cracked and cutting off angular areolae, 0.1–0.6 mm diam., the cracks narrow and shallow to gaping and deep, minutely wrinkled-papillate to rather crumbly, matt, without isidia, pruina, pseudocyphellae, or soredia. Cephalodia shallowly caespitose, round to irregular, 0.5–1 mm diam., projecting slightly above thallus surface, sometimes delimited from rest of thallus by narrow to gaping cracks, smooth to shallowly wrinkled to minutely cerebriform, not radiately grooved or cracked, translucent grey-blue to blackish when moist, grey-white to ivory and slightly glossy when dry, epruinose; cyanobiont Nostoc, in coiled chains, cells rounded, 3.5–6.5 μm diam. Apothecia scattered, sessile, often strongly constricted at base, round to irregular, 0.5–1(–1.5) mm diam., disc deeply concave, waxy, yellow-brown to pale red-brown, with a thin to thick, granular, white pruina; thalline margins persistent, slightly incurved, concolorous with thallus; proper margin very thin, slightly raised, concolorous with disc or darker. Epithecium dilute yellow-brown, 25–37.5 μm thick. Hymenium colourless, 175–200 μm tall. Hypothecium pale pinkish buff, nubilated, opaque, 150–175 μm thick. Asci cylindrical, 170–190(–250) × 30–37.5 μm, 4-spored. Ascospores closely uniseriate in ascus, oblong with rounded ends, (37–)40–57.5(–64) × 20–30 μm, walls smooth to 2 μm thick. Pycnidia scattered, swollen, nipple-like, 0.05–0.1 mm diam., clustered in small groups or solitary at margins, ostiole punctate-impressed, red-brown. Conidia filiform, straight or curved, 15–30 × 1 μm.

Chemistry : Stictic acid (major) and gyrophoric acid (tr.).

C: Known only from the type locality.

Endemic

Illustration : Galloway (2004b: 111, fig. 6).

Placopsis macrospora is characterised by: the saxicolous habit; the greyish to rusty-ochre thallus; deeply concave apothecia with waxy, yellow-brown to pale red-brown discs that are commonly white-pruinose; 4-spored asci; large, oblong ascospores, (37–)40–57.5(–64) × 20–30 μm, walls smooth to 2 μm thick; and stictic acid (major) and gyrophoric acid (tr.) as secondary metabolites. At present, it is known only from the type locality on Campbell I., where it associates closely with other species of Placopsis on subalpine rocks.