Australian Tropical Rainforest Orchids
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Arthrochilus oreophilus

Montane Elbow Orchid

Arthrochilus oreophilus D.L.Jones, Austral. Orch. Res. 2: 9-10, f. 8 (1991). Type: Queensland; Cook District; Herberton Range, 1724S, 14220E, 22 Jan 1988, L. Lawler 24 (holo CANB; iso BRI, CANB).

Distribution

Occurs in Queensland from Mt Finnigan near Cooktown to Evelyn Tableland.

Altitude: 800-1400 m.

Description

Terrestrial tuberous herb forming spreading colonies. Sterile plants a basal rosette of leaves only. Fertile plants an inflorescence with a rosette arising later from lateral stem at base of peduncle. Leaves 2-5, prostrate, ground-hugging, basal; lamina lanceolate, 2-4.5 cm x 1-1.8 cm, bluish-green above, paler beneath, margins entire to undulate, apex acute to acuminate. Infloresence a terminal raceme, erect, 88-200 mm long, dark reddish-brown, fleshy; pedicels obliquely erect, 3 mm long. Flowers 2-15, non-resupinate, erect to porrect, 12-20 mm long, green with brownish labellum glands. Dorsal sepal free, decurved, embracing basal third of column, narrowly obovate to spathulate, 9-10 mm x 2-2.5 mm, margins conduplicate, apex obtuse. Lateral sepals reflexed against the ovary, lanceolate, falcate, 6-7 mm x 2 mm, distal margins conduplicate, apex unequally emarginate. Petals reflexed against the ovary, linear, falcate, 6.5-7 mm x 1 mm, distal margins conduplicate, apex obtuse. Labellum free, recurved, 6 mm x 1 mm, hinged to underside of column foot by claw 0.5 mm long, base purplish, 1.6 mm wide, becoming green along lamina. Callus insectiform, proximally fused to lamina, 3.5 mm long; central area with crowded, shiny clubbed calli 0.3-0.6 mm long, reddish-brown; apex emarginate, c. 1.8 mm wide, with shiny black glands. Column incurved in a semi-circle, 7 mm long, inner surface shortly pubescent, with 2 pairs of column wings; proximal column wings projecting forwards, broadly triangular, falcate, 4 mm x 5 mm, translucent with few purple spots; distal wings smaller, linear, curved, 3 mm x 1 mm, divergent above anther. Column foot 3 mm long, apex anvil-shaped. Capsules erect, obovoid, 9 mm x 4 mm, dehiscent.

Ecology

Occurs in forests, woodlands and rainforest margins at higher altitudes, especially on slopes and ridges, favouring well-drained clay soils.

Relatively widespread and locally common.

Flowering period: November-January.

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