Flora of New Zealand Series

Holotype: New Zealand. Otago, Leith Valley below Morrison's Creek on rounded volcanic stones in bank of flood-prone stream, 30.vi.1993, P.N. Johnson 757 – CHR 494632. Isotype – MEL 1057470.

Description : Thallus crustose, epilithic, continuous to sparingly cracked, pale-silvery greyish green, smooth to minutely uneven, glossy to dull (older thalli), 30–100 μm thick, lacking a cortex, the uppermost 10 μm being free of photobiont. Prothallus not apparent. Perithecia semi-immersed to ±entirely immersed, moderately numerous, usually solitary; apex rounded or subconical; ostiole inconspicuous or in a shallow depression 60–100 μm wide. Involucrellum brown-black, dimidiate or extending to exciple base level, 0.42–0.82 mm diam, 50–100 μm thick. Centrum broadly ovate to depressed-ovate, 0.28–0.44 mm diam. Exciple uniformly hyaline, 20–35 μm thick. Paraphyses persistent, simple to very sparingly branched, not anastomosing, septate, 1–2 μm thick. Periphyses absent. Asci fissitunicate, 8-spored, cylindrical, 110–160 × 28–38 μm, apex rounded, 3–8 μm thick, with an ocular chamber 3–5 μm broad and 1–2 μm tall, convex to hemispherical, walls and apex IKI−, ascoplasm IKI + red-brown. Ascospores colourless, fusiform to elongate-fusiform, with 10–17 transverse septa, each loculus with 1–3 longitudinal or diagonal septa, apices rounded or ±pointed, with a gelatinous sheath 2–6 μm thick; irregularly biseriate, usually constricted at primary septum, 37–63 × 10– 19 μm. Pycnidia not seen.

S: Otago (Mt Cargill, Morrison's Creek). On shaded boulders on streamsides.

Endemic

Illustrations : McCarthy (1995e: 326, fig. 2); Malcolm & Galloway (1997: 111).

Strigula johnsonii is characterised by: the saxicolous habit; a very pale, mainly glossy thallus, large perithecia and, most signifcantly, ascospores that are larger and more richly septate than those of any other species. Named for Dr Peter N. Johnson of Dunedin, an avid collector of aquatic pyrenocarpous lichens.