Flora of New Zealand Series

≡Placodium illitum C.Knight, Trans. Linn. Soc. ser. 2, Bot. 1: 282 (1877).

≡Lecanora illita (C.Knight) Forssell, Bihang K. Sv. Vet.-Akad. Handl. 8 (3): 53 (1883).

Lectotype: New Zealand. Sine loco (prob. Wellington), Charles Knight – H-NYL 23848 [fide Lamb (1947: 267)]. Syntype material collected by Knight, in BM 8096, H, M, UPS, WELT L 6272, 6277 – [Knight's pencil drawing of asci used as illustration of his new species (see above) is preserved in WELT L6278].

Description : Flora (1985: 403).

Chemistry : Thallus K−, C+ red, KC+ red, Pd−; containing gyrophoric acid.

N: Gisborne (Maungaroa), Wellington (Ruapehu, Tararua Ra.). S: Nelson (Buller River, Maruia River, Inangahua Junction, Reefton), Westland (Fox Glacier, Karangerua River, Poerua River, Turiwhate, Haast River), Canterbury (Bealey River, Hawdon River, Havelock River), Otago (Hunter Valley, Earnslaw Burn, Dart River, Forgotten River), Southland (Homer, Hollyford Valley, Cascade Creek, Eglinton Valley, upper Oreti River, Spey River, Mararoa River, Monowai). A: (Carnley Harbour). C: On rocks and stones in riverbeds, glacial moraines, or rock outcrops in grassland at treeline, and on roadside banks and cuttings in high-rainfall areas. Commonly forming interlocking mosaics with several other species of Placopsis such as P. elixii, P. hertelii, P. lambii, P. perrugosa, P. polycarpa, P. pruinosa, and associating with the lichens Baeomyces heteromorphus, Gyalidea lecanorina, Porpidia macrocarpa, Stereocaulon corticatulum and S. colensoi.

Endemic

Illustrations : Knight (1877: pl. XXXVIII, fig. 13); Lamb (1947: pl. X, figs. 33, 34); Malcolm & Galloway (1997: 53, 104, 122).

Placopsis illita is characterised by: the thallus comprised of flat, interlocking, jigsaw-like areolae, olive-greenish to grey-green when wet, brownish grey when dry, occasionally rusty orange in sites rich in iron, smooth, matt, distinctly maculate (×10 lens); without isidia pruina, pseudocyphellae or soredia, bounded by a prominent, black, marginal prothallus, 0.5–1(–2) mm wide; widely scattered cephalodia, most common towards centre, orbicular, subconvex to somewhat flattened; sessile apothecia developed in concentric rings or radiating parallel lines towards centre of thallus, closely contiguous to discrete, round to irregular through mutual pressure, 0.5–1(–1.5) mm diam.; disc obscured by thalline margin at first, soon becoming plane to subconvex at maturity, translucent pinkish to red-brown (when young) to blue-purple at maturity when moist, black when dry, matt, slightly roughened, minutely cracked (×10 lens) to occasionally fissured in older fruits, epruinose, thalline margin prominent in young fruits, entire, pale-pinkish, translucent, minutely verruculose (×10 lens) concolorous with or paler than thallus, disappearing in older fruits; epithecium dark olive-brown to brown-black, 12–20 μm thick, granular; hymenium pale yellowish brown above to colourless, 80–140 μm tall; hypothecium yellow-brown to red-brown, opaque, 120–160 μm thick; asci cylindrical, 100–125 × 8–12 μm; and ascospores ellipsoidal, 13–15(–18) × (5–)6–7.5(–8.5) μm, contents vacuolate, pale rose-pink.