Flora of New Zealand Series

≡Dimerella flava Malcolm & Vězda, Folia geobot. phytotax. Praha 30: 315 (1995).

Holotype: New Zealand. South Island. Nelson, Brook Stream waterfalls, 41º19.3's, 173º17.5'E, 160 m, on Metrosideros diffusa 5.i.1995, W.M. Malcolm 1445 – CHR 413970. Isotype – Herb. A. Vězda.

Description : Thallus crustose, epiphyllous, continuous, olive-green, shiny, the prothallus not at all distinct, up to 0.5 mm thick, ecorticate. Photobiont green, Trentepohlia. Apothecia hypophyllous or rarely epiphyllous, orbicular, strongly constricted at base or subpedicellate, 0.8–1.0 mm diam., 0.25 mm high, pale-yellow, the disc plane, margins slightly elevated at first, soon excluded. Exciple coarsely paraplectenchymatous, hyaline. Hymenium hyaline, 50–55 μm tall. Paraphyses straight, simple, to 1.8 μm diam., apices swollen, capitate-globose, to 5 μm diam. Asci cylindrical. Ascospores uniseriate, ellipsoidal, 8–9 × 3 μm. Pycnidia epiphyllous, tubular, 1.2–1.75 mm tall, pale-yellow, tapering toward apex, 0.15 mm wide at base and 0.05 mm below apex, with a terminal club-shaped mass of pale-yellow conidia. Conidiophores 7–10 μm long, 1.5 μm wide, covering walls of the cavity in the basal part of the tube and producing copious conidia. Conidia, short-ellipsoidal, simple but often spuriously 1-septate, 3.3–3.5 × 1.8–2 μm.

S: Nelson (Brook Stream, Pelorus Bridge, Buller Gorge). On leaves of Beilschmiedia tawa and Blechnum colensoi. Known also from Brazil (W.M. Malcolm pers. comm.).

?Palaeotropical

Illustrations : Malcolm & Vězda (1995d: 316, fig. 1– as Dimerella flava); Malcolm & Galloway (1977: 177 – as Dimerella flava).

Coenogonium flavum is characterised by: the foliicolous habit; the relatively large, pale-yellow apothecia, soon immarginate, constricted at base or subpedicellate, mostly growing on underside of leaves or colonising thin twigs; and the remarkable, tapering, tubular pycnidia, pale-yellow as the apothecia, and clothing the photobiont-containing thallus on upper surface of leaves, rarely on thin twigs. Conidiophores line walls of basal cavity of the pycnidial tube, shedding copious conidia, which exude from the tip of the tube, characters not before seen in Coenogonium (Malcolm & Vězda 1995b: 316).