Flora of New Zealand Series

≡Placodium bicolor Tuck., Bull. Torrey Bot. Club6: 57 (1875).

Description : Thallus closely attached, lobate–crustose, rosette-forming to spreading thallus 2–5 cm diam. Prothallus absent. Lobes flat to convex, contiguous, separated by narrow cracks, 3–5 (–8) mm long, 1.5–2.5 mm wide, margins effigurate-plicate broadly rounded; centrally areolate, areolae 1–2.5 mm diam., plane to subconvex, separated by deep and sometimes gaping cracks. Upper surface conspicuously rusty orange-yellow to red-brown, pale at margins, matt, without isidia, pruina or soredia. Cephalodia sessile, ±flush with upper surface, 2–6(–8) mm diam., plicate-effigurate and distinctly radially cracked, purplish black when wet, concolorous with thallus when dry. Apothecia scattered, sessile, constricted at base, solitary, rounded, (0.5–)1–2 mm diam. Thalline margin persistent, thin, entire or radially cracked, concolorous with thallus or paler. Disc plane, dark brown-black, epruinose. Epithecium olive-brown, 15–20 μm thick. Hymenium colourless, 160–240 μm tall. Ascospores uniseriate in ascus, broadly ellipsoidal, (18–)20–24 × 10–15 μm. Pycnidia immersed in thalline swellings, ostiole dark-brown to black. Conidia thread-like curved to ±straight, 18–24(–33) × 0.5 –1 μm.

Chemistry : Thallus K−, C+ red, KC−, Pd−; containing gyrophoric acid (major) and lecanoric acid (minor).

N: Wellington (Tongariro National Park). S: Canterbury (Arthur's Pass National Park, Temple Basin, Phipps Peak, Tawera, Woolshed Hill, Mt Misery Creek, Mt Torlesse, Two Thumbs Peak, Ben Ohau Ra., Upper Cass River, Lake Tekapo), Otago (Scratchback Hill, Flagstaff), Southland (S branch Aparima River, Takitimu Mountains, Dusky Sound, above Cascade Cove). On subalpine to exposed high-alpine rocks. Known also from southern South America, Kerguelen, the Crozet Archipelago, Heard I., and Prince Edward Is (Lamb 1947; Dodge 1948; Galloway 2002a; Hertel 2003; Øvstedal & Gremmen 2006).

Austral

Illustrations : Lamb (1947: pl. I, figs 2, 3).

Placopsis bicolor is characterised by: the rusty orange thallus without a marginal prothallus; and the absence of soralia.