2n = 36

2n = 36

2n = 36

Summer-green, terrestrial, glabrous, tuberous herb forming extensive colonies. Leaf solitary, fleshy, shortly-petiolate; usually spreading and held flat to the ground surface; lamina 20-40 × 15-35 mm, sometimes larger, ovate-oblong or broadly wedge-shaped, often pandurate, squared and apiculate at tip, with apiculus decurved, rounded and cordate at base; midrib grooved above, ridged beneath; leaf colour dull dark green above and often purple-spotted on margins, on midrib, or overall, silvery and pellucid beneath. Petiole 3—5(—10) × 1.5—3 mm, winged. Flowers usually solitary, rarely two, 12—20 mm long, dark red-green, dominated by the labellum, dorsal sepal, and long filiform petals and lateral sepals, on a peduncle 4-5 mm long. Ovary 4—8 mm long, green or whitish and purpleflecked, curved, subtended by two unequal floral bracts, the smaller 3—5 mm long, linear-subulate, terete, the larger equal to or exceeding the ovary, 7— 10 mm long, lanceolate, green with purple flecks. Dorsal sepal extending well past labellum, 20—35 × 8—12 mm, narrowly ovate in outline when flattened, concave, cucullate and arching over labellum tube, with tip often recurved, green with purple spots and striations; veins ridged. Lateral sepals 50-70 × 0.5— 1.0 mm at widest point, filiform, greatly exceeding labellum, whitish with purple striations, suberect to erect and projecting forwards, channelled, twisted, and connivent at expanded base. Petals 40-60 × 0.5— 1.0 mm at widest point, usually shorter than lateral sepals but not greatly so, filiform, greatly exceeding labellum, whitish with purple striations, horizontal to suberect and projecting forwards and outwards, channelled, auriculate on the base of the column. Auricles short, projecting downwards and forwards, with apertures 1.5—2.5 mm across. Labellum conspicuous, dark red almost black throughout, sometimes greenish-streaked at front, strongly iridescent when wet; labellum tube 5—7 mm long, erect, then abruptly deflexed through 160-180° and expanding into the lamina, with a prominent bead-like callus in throat of tube at the bend; lamina 10—20 × 10— 15 mm, broadly ovate to orbicular; upper margins folded inwards, joining or overlapping; lower surface spreading, deflexed against ovary, with margins erose-papillose, and a long median apiculus; inner surface with dense, minute, retrorse papillae and ridged veins; throat of labellum tube high on lamina. Column 3—4 mm long, broadest and ridged at base, inclined backwards, minutely winged. Stigma shield-shaped to oblong, c. 1.0 mm across, concave; margins fimbriate. Anther c. 1.0 mm, obtuse, purpleflecked, with papillose margins; pollinia 4, united in pairs, c. 1.0 × 0.7 mm, oblong, mealy, yellow; viscidium c. 0.5 mm across, oblong to orbicular, concave with thickened edges, at first translucent white, later light brown. Capsule 12—15(—20) × 5- 7 mm, elliptic, at first pale green, later brown, on a greatly elongated peduncle. Tuberoids globose to ellipsoid on extended roots. FLOWERING: August to October. Plants in the wild and in cultivation flower annually though varying in intensity from year to year. Pollination appears to be wholly insect-dependent. Fungus gnats (Mycetophila spp.), some with pollen attached to the thorax, have been observed entering and leaving flowers of C. iridescens grown in cultivation (Fuller 1980, 1994; B. P. J. Molloy pers. obs.), and some of these flowers have subsequently developed seed capsules. However, the pollination biology of C. iridescens needs to be confirmed experimentally (see especially Godley 1979). FRUITING: September to November. Capsules develop rapidly after fertilisation, and are carried upwards on greatly elongated peduncles as they approach maturity. Most mature capsules examined were well filled with apparently sound seed that is dispersed by wind, water, or gravity following capsule dehiscence.

C. macrantho similis a quo foliis breviter petiolatis plerumque maculatis, sepalo dorsali latiore, petalis sepalisque Iateralibus subaequalibus, labello abrupte deflexo atrorubro paene nigro iridescenti ubi madido, callo prominenti ad labelli tubi orificium, et maturio anthesis intio differt.