Flora of New Zealand Series

Holotype: New Zealand. Nelson, Brook Stream Track, 41º19.1's, 173º17.6'E, 130 m, on tree-shaded siliceous rock in disturbed lowland forest, 22.x.1995, W.M. Malcolm 2623 – CHR 507219. Isotype – CANB.

Description : Thallus crustose, epilithic, pale- to medium-green, determinate, continuous to rimose, matt to slightly glossy, smooth to minutely uneven, 30–80 μm thick, ecorticate; prothallus thin, dark-grey to black. Photobiont Trentepohlia. Perithecia numerous, semi-immersed to ±superficial, usually partly to entirely covered by a thalline layer 20–60 μm thick; apex dull black, usually rounded; ostiole inconspicuous. Involucrellum black, 0.23–0.35(–0.4) mm diam., 30–50 μm thick at apex, 70–130 μm thick and spreading at base, often subtending exciple. Exciple dark-brown to blackish, 12–25 μm thick. Centrum globose to depressed-ovate, 0.17–0.24 mm diam. Paraphyses simple to very sparingly branched, 1–1.5(–2) μm thick. Periphyses absent. Subhymenium c. 20 μm thick. Asci fissitunicate, elongate-clavate, 78–92 × 11–14 μm, apex rounded or subacute, ocular chamber minute, convex to tubercular, visible only in immature asci. Ascospores colourless, elongate-fusiform, 1-septate, 22–32 × 4–6.5 μm, constricted at septum, lacking appendages; apices usually bluntly pointed, occasionally rounded, rarely apiculate; cells similar or distal cell longer and slightly broader than proximal cell, usually separating at or after dehiscence; demispores (10.5–)14(–18) × (4–)5(–6.5) μm, contents clear or guttulate. Pycnidia numerous, semi-immersed, black, 60–120 μm diam. Microconidia elongate-ellipsoidal to fusiform, 2–3 × 0.7–1 μm. Macroconidia not seen.

S: Nelson. Known only from the type locality.

Endemic

Illustrations : McCarthy & Malcolm (1996b: 324, fig. 1); Malcolm & Galloway (1997: 162, 180); Malcolm & Malcolm (2000: 79).

Strigula occulta is characterised by: the saxicolous thallus; broader perithecia that are partly or almost entirely overgrown by the thallus; the dark exciple; discontinuously longer asci; broad ascospores; and small microconidia. The related S. taylori (Carroll ex Nyl.) R.C.Harris and its allies from Europe and North America have a well-defined thallus, small perithecia and elongate, 1-septate ascospores that commonly fracture at the septum.