Leafless terrestrials with fleshy subterranean rhizomes bearing thin apical roots and short, erect, scapes which carry 1-2 porrect, inflated, brownish or yellowish, stalked, bell-shaped flowers. The sepals and petals are fused together with the tips free, completely enclosing the column and labellum. The labellum has a short narrow basal part with 2 warty calli at the base and is then broadly flared with smooth margins and 2 narrow smooth apical ridges. The column is relatively broad with long wings, a basal stigma and very short column foot.
Significant Generic Characters
Leafless mycotrophic terrestrial orchids; rhizomes fleshy, subterranean, horizontal, with filamentous roots from the apex; inflorescence terminal, 1-2-flowered; peduncle brownish; flowers resupinate, campanulate, brownish or yellowish; sepals and petals fused with the tips free, enclosing the labellum and column; labellum attached to the apex of the column foot and bases of lateral sepals; lamina with a short, narrow, basal hypochile bearing 2 densely tuberculate calli and an expanded smooth epichile; callus bearing 2 narrow, relatively tall, smooth ridges near the labellum apex; column with a very short foot; stigma basal; pollinia 2, coarsely sectile.
Size and Distribution
A genus of about 5 species distributed in Indonesia, New Guinea and Australia where there is a single endemic species, D. queenslandica, restricted to northeastern Queensland between the McIlwraith Range on Cape York Peninsula and near Babinda. State occurrence: Queensland.
Demorchis queenslandica grows among litter in dense rainforest, mainly in the lowlands but extending to about 450 m alt. Because of their cryptic nature flowering plants are rarely seen with most records being of fruiting plants with their capsules extended above ground. The whole flowering/fruiting cycle is rapid with plants only being above-ground for 1-2 weeks.
Pollination: The flowers of Demorchis queenslandica are self-pollinating.
Reproduction: Reproduction in Demorchis queenslandica is solely from seed. Seed dispersal takes 7-14 days from pollination and the capsules develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: Plants of Demorchis queenslandica survive as subterranean rhizomes with the inflorescence the only part to emerge above ground.
Flowering: Demorchis queenslandica flowers November to January.
Hybrids: Natural hybrids involving Demorchis queenslandica are unknown.
Fire: Demorchis queenslandica does not occur in fire-prone habitats.
The name Demorchis is derived from the Greek demos, plump, fat, and Orchis, another genus of Orchidaceae, but also applied generally to orchids; reference to the plump flowers.
Perennial, leafless, geophytic herbs, mycotrophic, sympodial. Plants glabrous. Rhizomes fleshy, subterranean, thin, elongate, smooth, single, mostly horizontal, lasting many years. Roots filamentous, arising from the apex of the rhizome. Stem absent. Trichomes absent. Leaves absent. Inflorescence racemose, terminal, 1-2-flowered. Peduncle longer than the rhachis, thin, brownish. Sterile bracts semi-tubular, base sheathing. Floral bracts very small, sheathing. Pedicel short, thin, distinct from the ovary. Ovary straight, smooth. Flowers resupinate, campanulate, brownish or yellowish, porrect, lasting 1-2 days. Perianth segments thick, fleshy, connate throughout with free tips, smooth. Dorsal sepal fused with the lateral sepals and petals, similar to the lateral sepals, concave. Lateral sepals fused with the dorsal sepal and petals, similar to the dorsal sepal, concave, externally keeled, sometimes with an internal rugose area near the apex. Petals small, fused with the sepals, the tips free. Labellum attached to the apex of the column foot and partly fused with the bases of the lateral sepals, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina divided into a hypochile and epichile; hypochile short, narrow, with 2 densely tuberculate basal calli; epichile broadly expanded, with smooth margins; ventral surface smooth; apex narrow. Spur absent. Callus consisting of 2 short, tall, narrow, smooth ridges near the labellum apex. Nectar unknown. Column porrect from the end of the ovary, relatively long, fleshy, lacking free filament and style. Column wings running the length of the column, extending above the anther as narrow stelidia. Column foot short. Pseudospur absent. Anther terminal, incumbent, rostrate. Pollinarium absent. Pollinia 2, narrow, deeply grooved, often fragmenting, coarsely sectile, yellow. Viscidium absent. Rostellum flat, entire, plate -like, projecting. Stigma basal, concave. Capsules dehiscent, smooth, erect; peduncle elongated in fruit; pedicel elongated in fruit. Seeds numerous, light coloured, winged.
Demorchis was recently segregated from Gastrodia (Jones and Clements 2004).
Demorchis is distinguished from Gastrodia by the presence of filamentous roots which arise from the apex of the rhizome, short inflated flowers with thick fleshy sepals, hypochile with 2 tuberculate basal calli, column winged throughout with free apical stelidia extending above the anther and the peduncle and pedicel thickening and increasing in length after fertilisation.
Demorchis D.L.Jones and M.A.Clem., Orchadian 14(8): Scientific Supplement xiii (2004).
Dockrill, A.W. (1969). Australian Indigenous Orchids. Volume 1. The Society for Growing Australian Plants, Halstead Press, Sydney.
Dockrill, A.W (1992). Australian Indigenous Orchids. Volume 1 & 2. Surrey Beatty & Sons in association with the Society for Growing Australian Plants, Chipping Norton, NSW.