Epiphytes or lithophytes anchored by roots that arise from nodes at the base of a pseudobulb. Rhizomes very short, indiscernible. Pseudobulbs hard, elongated, narrow at the base, more or less cylindrical. Leaves arising on the apical nodes, longer than wide, flat or shallowly concave, without any channel or groove, basally sheathing; apex unequally notched. Racemes short, from the upper nodes. Flowers lasting many days, moderately small, firm-textured. Perianth segments flat. Dorsal sepal smaller than the lateral sepals. Bases of the lateral sepals fused with the column foot. Petals shorter than the sepals. Labellum stiffly attached to the apex of the column foot. Labellum lamina distinctly three-lobed; lateral lobes moderately large; midlobe broad, notched. Callus with prominent central ridges. Labellum base, column foot and lateral lobes forming a short basal pseudospur.
Significant Generic Characters
Epiphytic/lithophytic orchids; rhizomes indiscernible; pseudobulbs hard, more or less cylindrical; leaves lasting 1-3 seasons, restricted to apical nodes, longer than wide, flat or shallowly concave, sheathing basally; racemes short, from the upper nodes; flowers moderately small, long-lasting; perianth segments flat; dorsal sepal smaller than the lateral sepals; lateral sepals bases fused with the column foot; petals shorter than the sepals; labellum stiffly attached to the apex of the column foot; lamina three-lobed; lateral lobes moderately large; midlobe broad, notched; callus with prominent central ridges; pseudospur formed from labellum base, column foot and lateral lobes.
Size and Distribution
A genus of about 5 species distributed in New Caledonia and north-eastern Queensland where there is a single endemic species. The Australian species, Eleutheroglossum fellowsii, is restricted to the ranges and tablelands between Mt Finnigan (15°50' S) and the Paluma Range (19°10' S) near Townsville. State occurrence: Queensland.
Ecology
Eleutheroglossum fellowsii occurs on the branches of rough-barked or flaky-barked trees along rainforest margins, in wet sclerophyll forest and beside streams in open forest, in situations of bright light and with free air movement. 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, particularly localised coastal showers.
Biology
Pollination: The flowers of Eleutheroglossum fellowsii, which last several days, are insect-pollinated but the vector is unknown.
Reproduction: Reproduction in Eleutheroglossum fellowsii is solely from seed. Seed dispersal takes 4-6 months after pollination and the capsules develop in a pendulous 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 in summer.
Hybrids: Natural hybrids involving Eleutheroglossum fellowsii in Australia are unknown.
Derivation
Eleutheroglossum, which is derived from the Greek eleutheros, free and glossum, lip, refers to the hinged labellum.
Botanical Description
Perennial, deciduous, epiphytic or lithophytic herbs, sympodial. Plants glabrous. Roots elongate, produced from nodes on the base of the pseudobulb. Rhizome superficial, branched. Pseudobulbs well-developed, crowded, hard, elongate, thickened in the distal half, when young covered by scarious bracts. Trichomes absent. Aerial growths absent. Leaves lasting 1-3 seasons, distichous, restricted to apical nodes, sessile, much longer than wide, moderately thick, coriaceous, smooth, not grooved or channelled; base sheathing the pseudobulb; margins entire; apex unequally emarginate. Inflorescence racemose, erect to arcuate, arising from an apical node on a mature pseudobulb, few-flowered. Peduncle about as long as the rhachis, the base with imbricate scarious bracts. Floral bracts scarious, small, subtending the base of the pedicel. Pedicel relatively long, thin, merging with the ovary. Ovary short, straight or curved. Flowers resupinate, stalked, lasting a few days, green, brown or white; labellum with distinct striae or coloured veins. Perianth segments firm-textured, widely spreading, entire, straight. Dorsal sepal free, smaller than the lateral sepals; apex entire, flat. Lateral sepals larger than the dorsal sepal, attached by their bases to the column foot; apex entire. Petals free, narrower than the sepals, about as long as the dorsal sepal; apex entire. Labellum stiffly attached 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, strongly three-lobed; lateral lobes moderately large, erect, flanking the column, entire; midlobe broad, porrect to recurved; apex deeply notched, the lobes spreading or erect. Spur absent. Callus consisting of narrow parallel ridges, enlarged and irregular on the midlobe. Nectar absent. Column lacking free filament and style, fleshy, much shorter than the perianth segments, nearly straight. Column wings present, reduced, ventral and with short tooth-like apical stelidia. Column foot well developed, as long as or longer than the column, straight or curved. Pseudospur present, formed by the elongated base of the labellum, the column foot and bases of the lateral sepals. Anther terminal, incumbent, 2-celled, persistent, attached dorsally by a ligulate claw, smooth, erostrate; apex smooth. Pollinarium absent. Pollinia 4 in 2 pairs, straight or falcate, yellow or orange, hard, waxy. Viscidium absent. Rostellum ventral, swollen, transverse. Stigma entire, transverse, concave. Capsules dehiscent, large, glabrous, pendulous; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, relatively large, light coloured, winged.
Taxonomy
Eleutheroglossum was originally included as a section within Dendrobium (Jones & Clements 2002).
Nomenclature
Eleutheroglossum (Schltr.) M.A.Clem. & D.L.Jones, Orchadian 13(11): 489 (2002); Dendrobium section Eleutheroglossum Schltr., Bot. Jahrb., 39: 48 (1906). Type species: Dendrobium eleutheroglossum Schltr. [Eleutheroglossum jocosum (Rchb.f.) M.A.Clem. & D.L.Jones].
References
Clements, M.A. & 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). The Orchidaceae of German New Guinea (English translation by R.S. Rogers, H.J. Katz and J.T. Simmons). Australian Orchid Foundation, Melbourne.