Button Orchids
Epiphytic or lithophytic orchids with prominent, thick, creeping, branched rhizomes anchored by filamentous roots that arise from rhizome nodes. Pseudobulbs absent. Leaves thick, fleshy, arranged alternately along the rhizomes, stalked, without any channel or groove, ranging from as wide as long to longer than wide, with a pustulate or pitted surface. Flowers borne singly at sporadic intervals from a multi-flowered inflorescence that arises from the base of a pseudobulb, lasting 2-3 days, relatively small, thin-textured, with no apparent scent. Lateral sepal bases fused with the column foot. Petals smaller than the sepals. Labellum stiffly hinged to the apex of the column foot. Labellum lamina very obscurely three-lobed, relatively thick and fleshy, the basal margins thickened and papillate.
Similar Genera
Significant Generic Characters
Epiphytic/lithophytic orchids; rhizomes thick, creeping, branched; pseudobulbs absent; leaves lasting several seasons, alternate, stalked, thick, fleshy, not grooved, pustulate; inflorescence perennial, arising at the base of a pseudobulb; flowers borne singly at sporadic intervals, each lasting 2-3 days; lateral sepal bases fused with the column foot; petals smaller than the sepals; labellum stiffly hinged to the apex of the column foot; lamina obscurely three-lobed, fleshy, with thickened papillate basal margins.
Size and Distribution
A small genus of 3 species endemic in north-eastern Queensland between the Big Tableland south of Cooktown (15°42' S) and Mt William west of Mackay (21°02' S) at altitudes between 600 and 1200m. State occurrence: Queensland.
Ecology
Species of Davejonesia grow in highland areas of the ranges and tablelands. They occur on trees and rocks in moist or humid habitats, including rainforest, open forest and woodland. The climate is tropical and the majority of rain falls during the summer wet season (December to March), with the remaining months much drier and having sporadic or intermittent rain. Fogs and mists are frequent at higher altitudes.
Biology
Pollination: The flowers of species of Davejonesia last for 2-3 few days and are pollinated by small native bees.
Reproduction: Reproduction in Davejonesia is solely from seed. Seed dispersal takes 4-6 months after pollination and the capsules develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: The plants grow actively during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Flowering occurs sporadically throughout the year.
Hybrids: Natural hybrids involving species of Davejonesia are unknown.
Derivation
Davejonesia is named after David L. Jones (1944-), contemporary Australian botanist specialising in Australian Orchidaceae.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs, sympodial. Plants glabrous. Roots filamentous, produced from nodes along the rhizome. Rhizomes closely appressed to the host, well-developed, sturdy, creeping, branched, covered by closely sheathing, imbricate, scarious bracts. Pseudobulbs absent. Trichomes absent. Leaves lasting several seasons, petiolate, not sheathing at the base, ranging from as wide as long to longer than wide, not grooved or channelled, thick and fleshy, coriaceous, pustulate or pitted, when young covered by scarious bracts; apex entire. Inflorescence arising from the base of a mature pseudobulb, multiflowered but each flower arising singly at sporadic intervals. Peduncle longer than the pedicel, erect, the base covered with imbricate scarious bracts. Floral bract scarious, sheathing the base of the ovary. Pedicel absent or vestigial, merging with the ovary. Ovary short, straight. Flowers resupinate, stalked, lasting 2-3 days, cream or pinkish with a contrasting yellow labellum. Perianth segments thin-textured, spreading. Dorsal sepal free, subsimilar to the lateral sepals; apex entire, flat. Lateral sepals subsimilar to the dorsal sepal, attached by their bases to the column foot; apex entire. Petals free, smaller than the sepals; apex entire. Labellum stiffly hinged to the apex of the column foot, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina more or less oblong, fleshy, very obscurely three-lobed; basal two-thirds flat, with thickened margins that are papillate; midlobe fleshy, yellow; apex entire. Spur absent. Callus obscure. Nectar absent. Column lacking free filament and style, short, nearly straight. Column wings present, ventral and with short tooth-like apical stelidia. Column foot well developed, curved. Pseudospur formed by the bases of the lateral sepals and the column foot. Anther terminal, incumbent, 2-celled, persistent, attached dorsally by a ligulate claw, smooth, erostrate. Pollinarium absent. Pollinia 4 in 2 pairs, falcate, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, transverse. Stigma entire, transverse, concave. Capsules dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Davejonesia, a recent segregate from Dockrillia, has also been included in Dendrobium (Jones and Clements 2002).
Nomenclature
Davejonesia M.A.Clem., Orchadian 13(11): 487 (2002). Type species: Dendrobium lichenastrum F.Muell. [Davejonesia lichenastrum (F.Muell.) M.A.Clem.].
Dockrillia Brieger sect. Lichenastrum Brieger in Schltr., Die Orch. (ed. 3) 1: 746 (1981).
Infrageneric Taxa: No infrageneric taxa are currently recognised.
References
Clements, M.A. and Jones, D.L. (2002). Nomenclatural changes in the Australian and New Zealand Bulbophyllinae and Eriinae (Orchidaceae). Orchadian 13(11): 498-501.
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.
Schlechter, R. (1982 English translation). The Orchidaceae of German New Guinea, Australian Orchid Foundation.