Flora of New Zealand Series

Holotype: New Zealand. Wellington, Erua near National Park, on shrub, 16.xii.1977, J.K. Bartlett 18579 – LG. Isotypes – CANB, CHR.

Description : Thallus foliicolous, subcuticular (along nerves, or at leaf margins or along tears or scars), ±circular 2–5 mm diam., abundant, pale-green or olive-brown (white when moribund), glossy, surface smooth, of dichotomously branching, narrow (0.1 mm wide) lobes, fusing laterally and forming a reticulum, margins with a discontinuous to continuous black, prothalline line and with numerous, small, elongate black papillae (×10 lens). Photobiont Cephaleuros with ± rectangular or rounded cells, 8–15 × 4–7 μm, yellow-green arranged in radiating rows. Perithecia abundant, typically at centre of small, circular (0.3–0.6 mm diam.) islands of thallus at or near lobe margins, solitary or 2–3-together, hemispherical, black, glossy, 0.20–0.25 mm diam., 0.10–0.18 mm tall, immersed in thallus to ⅓ of total height. Ostiole not apparent. Involucrellum heavily carbonised, outer wall black, 28–40 μm thick near ostiole, not or scarcely expanding laterally, outer wall absent under perithecial cavity, inner wall pale-brown, indistinct. Centrum 120–140 × 160–180 μm. Paraphyses branched and anastomosing, c. 1 μm thick. Asci clavate, 55–60 × 10–14 μm, with thickened apex containing a small ocular chamber. Ascospores 8 per ascus, biseriate in ascus, ellipsoidal to fusiform, apices rounded, 1-septate, slightly constricted at septum, walls 0.7–1 μm thick, the proximal cell slightly longer, not breaking at septum and lacking gelatinous terminal appendages, 15–16(–18) × 4.5–5 μm. Pycnidia of two kinds: (1) flattened to hemispherical, 0.1 mm diam., solitary or 2–4-together, elongate, typically developed at margins of lobes producing macroconidia, oblong with rounded ends, 1-septate, not or slightly constricted at septum, 13–16 × 3–3.5 μm, with elongate, 3–5 μm long, gelatinous appendages at both or one end; (2) tiny black points at margins of thallus (or included in pycnidia with macroconidia) producing microconidia, ellipsoidal, ±deformed with rounded ends, 3 × 1 μm.

N: Northland (Herekino Gorge, Church Road Scenic Reserve near Kaitaia, Ngaiotonga Saddle), Wellington (Erua). On leaves of Beilschmiedia tawa. The type material, and all other published records, collected by the late John Bartlett (Sérusiaux 1998a: 150).

Endemic

Illustrations : Sérusiaux (1998a: 148, figs. 1–2; 149, fig. 7A–B).

Strigula delicata is characterised by: the foliicolous habit; a thallus of dichotomously branched lobes forming an attractively patterned reticulum; hemispherical perithecia developing on tiny circular islands of thallus at lobe margins; ascospores with thick walls; and rather long macroconidia, 13–16 × 3–3.5 μm. Two different growth forms occur: (1) with dichotomously branched, sparingly anastomosing lobes and a pale-green thallus; (2) with a more compact thallus forming an attractive reticulum of anastomosing lobes and an olive-brown thallus. Perithecia, asci, ascospores and conidia are identical in both forms, the observed differences in morphology being possibly the result of differing host leaf characteristics.