Flora of New Zealand Series

≡Lecanora (Placopsis) tararuana Zahlbr., Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 348 (1941).

Holotype: New Zealand. Wellington, Tararua Mountains, Table Top, on rock in forest, c. 800 m, ix.1933, E. Chamberlain 189 – W696.

Description : Thallus crustose, very closely attached, thin, film-like (0.1–0.4 mm thick), dark-green when wet, pale whitish green when dry, delicately white-maculate in both wet and dry states (×10 lens), 1–5(–10) cm diam., forming mosaics; delimited by a very narrow, wavy, black hypothalline line at margins, most noticeable at junctions of intersecting thalli. Surface smooth or minutely undulate or papillate in parts, matt or roughened, continuous to effigurate-cracked, cracks narrow, 0.05–0.2(–0.3) mm wide, white medulla exposed at base of widest cracks, 0.05–2(–4) mm long, simple, furcate or here and there subreticulate, becoming continuous around cephalodia and apothecia; without isidia, pruina, pustules or soredia. Cephalodia immersed in thallus, level with thallus surface to very shallowly convex and just elevated above thallus surface, round to ovoid or subirregular, (0.5–)1–3(–4) mm diam., surrounded by a narrow crack, surface plane to somewhat minutely lumpy or minutely wrinkled (×10 lens), never plicate-radiate or furrowed, occasionally with one or two, short, irregular cracks at maturity, pale-pinkish, opaque when dry, puplish blue, translucent when wet. Apothecia widely scattered, rather sparse, sessile, round, 0.5–1(–1.2) mm diam., solitary or occasionally 2–3-together, usually delimited by a narrow crack in the thallus; proper exciple narrow, pale pinkish white when dry and contrasting with disc, translucent when wet; thalline exciple minutely scabrid (×10 lens) to crenulate or minutely papillate, pale pinkish white above and concolorous with thallus below; disc plane to shallowly concave, smooth to minutely roughened (×10 lens), pale-pink to red-brown, epruinose. Epithecium minutely granular–nubilated, pale yellow-brown, 25–33 μm thick. Hymenium colourless, 200–250(–300) μm tall. Hypothecium pale yellow-brown, opaque, 200–250 μm thick. Paraphyses simple, unbranched, 2.5–3.5 μm thick, apices not swollen or moniliform. Asci cylindrical, 160–170 × 20–25 μm. Ascospores colourless, uniseriate in ascus, ovoid to broadly ellipsoidal, apices rounded or slightly pointed, 20–25(–27) × 10–12.5(–15) μm. Pycnidia minutely papillate, 0.01 mm diam., or less, pale red-brown, widely scattered or clustered in small groups at margins and centrally, ostiole darker, punctiform-depressed. Conidia filiform, 23.5–28.5 × 1 μm.

Chemistry : Cortex K−; medulla K−, C−, KC−, Pd−. TLC nil.

N: Wellington (Tararua Ra.). S: Nelson (Mt Arthur, Denniston Plateau, Springs Junction), Westland (Nr Greymouth, Lake Wombat), Otago (Matukituki Valley, Rockburn Valley, Sugarloaf Saddle, Survey Flat Dart River), Southland (George River, George Sound, near Supper Cove Dusky Sound). On rocks in shaded, habitats of high humidity, forming mosaics, often with other species of Placopsis (viz. P. argillacea, P. cribellans, P. dusenii, P. gelida and P. macrophthalma) and with Gyalidea hyalinescens and Parmeliella nigrocincta.

Endemic

Placopsis tararuana is characterised by: the thin, crustose, dark-green thallus which is continuous to minutely and irregularly effigurate-cracked; by the round to oval, ±immersed cephalodia delimited by a ±continuous crack and having a plane to minutely lumpy or wrinkled surface (never plicate-ridged or -furrowed or radiate-cracked); by the small, scattered, sessile apothecia; and by the ovoid to broadly ellipsoidal ascospores, 20–25(–27) × 10–12.5(–15) μm.