Ribbonroot Orchids
Leafless epiphytes with a very short stem and spreading roots, round, flat or triangular in cross-section, smooth or warty, grey or greenish. Inflorescences are short, thin, unbranched with small, flat or tubular flowers that last from a few hours to a few days and are produced one at a time in spasms. The labellum, which is fixed to the column base, has a prominent basal spur, small to large lateral lobes and a narrow projecting midlobe. The column is very short without a foot.
Similar Genera
Significant Generic Characters
Leafless epiphytic/lithophytic orchids; roots round, flat or triangular in cross-section, smooth or verrucose, green or greyish, photosynthetic; stems very short; leaves absent; inflorescence racemose; flowers small, flat or tubular, opening singly in spasms; perianth segments thin-textured, free or basally fused; sepals and petals subsimilar or dissimilar; labellum fixed to the column base; lamina unlobed or 3-lobed, with a basal spur; lateral lobes vestigial to well-developed; midlobe well-developed, narrow, porrect; callus vestigial or absent; column very short, without a foot at right; pollinia 4, free, sessile on a stipe.
Size and Distribution
A genus of about 170 species, 9 species occurring in Australia, including 1 species each on Norfolk Island and Christmas Island. On the mainland the Australian species are distributed in Queensland and New South Wales, between Cape York (about 17º16' S) and areas to the west of Wauchope (about 32º28' S). State occurrence: Queensland, New South Wales (including Norfolk Island), Western Australia (Christmas Island).
Ecology
The native species of Taeniophyllum grow on shrubs and trees, rarely on rocks, in rainforest, moist areas of open forest, streamside vegetation, swamps, moist gullies and gorges. Most species grow where there is free and unimpeded air movement. In rainforest the plants are often found on twigs of the outer canopy.
Biology
Pollination: The flowers of Taeniophyllum from last a few hours to a few days and are produced singly in spasms. Some species are self-pollinating, others are insect-pollinated but the vector is unknown.
Reproduction: Reproduction in Taeniophyllum is solely from seed. Seed dispersal takes 10-12 months after pollination and the capsules develop in a porrect position. Apomixis is unknown in the genus.
Seasonal Growth: Plants of Taeniophyllum grow mainly during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Taeniophyllum species flower in spring, summer and autumn.
Hybrids: Natural hybrids involving the native species of Taeniophyllum are unknown.
Derivation
Taeniophyllum, which is derived from the Greek tainia, fillet and phyllon, leaf, refers to the ribbon-like roots which are photosynthetic and take the place of leaves.
Botanical Description
Perennial, leafless, epiphytic or lithophytic herbs, monopodial. Roots narrow to broad, flat, round or triangular in cross-section, smooth or verrucose, greyish or greenish, sometimes with white lenticels, photosynthetic, adherent. Plants unbranched. Stem very short, fibrous. Pseudobulbs absent. Trichomes present or absent. Leaves absent, sometimes a persistent isobilateral protocorm persistent at the meristem. Venation unknown. Inflorescence lateral, racemose, arcuate, multiflowered. Peduncle shorter, similar or longer than the rhachis, thin, wiry; sterile bracts mainly basal, small, scarious, persistent or caducous. Rhachis thin, straight or flexuose, sometimes abbreviated and greatly compressed, sometimes laterally flattened, elongating as flowering progresses. Floral bracts small, scarious, sheathing the base of the pedicle, sometimes imbricate, sometimes distichous. Pedicel short, very thin, merging with the ovary, glabrous or hirsute. Ovary short, straight, glabrous or hirsute. Flowers opening singly, resupinate, small, stalked, tubular or opening widely, lasting a few hours to a few days, green or yellowish, sometimes fragrant. Perianth segments free or fused basally, thin-textured, narrow, porrect to spreading. Dorsal sepal free or proximally fused with the petals and/or lateral sepals, broader than or subsimilar to the lateral sepals. Lateral sepals free or proximally fused with the petals and/or lateral sepals, narrower than or subsimilar to the dorsal sepal. Petals free or proximally fused with the sepals, smaller than the sepals. Labellum fixed to the column base, markedly dissimilar in size and shape to the sepals and petals, calcarate. Labellum lamina unlobed or 3-lobed, sometimes semi-tubular, with a basal spur; spur long and cylindrical or short and saccate, without calli; lateral lobes vestigial to well-developed, entire, erect or incurved; midlobe porrect, narrow, flat or semi-tubular, the apex sometimes with an erect dentiform or filiform appendage. Spur present (see labellum lamina). Callus vestigial or absent. Nectar present or absent. Column very short, porrect from the apex of the ovary or at a slight angle, lacking free filament and style, fleshy. Column wings vestigial to well-developed, ventral. Column foot long, at right angles to the column. Pseudospur absent. Anther terminal, incumbent, 4-celled, persistent, smooth, with a short to long rostrum. Pollinarium present. Pollinia 4, free, equal or unequal, orange, hard, waxy, sessile. Stipe short to long, relatively broad. Viscidium short to long, narrow to broad, at an angle to the stipe. Rostellum short, bifid. Stigma entire, deeply concave. Capsules dehiscent, glabrous or hirsute, porrect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Within the Vandeae, Taeniophyllum is characterised by leafless habit; very short stems; spasmodic flowering; small tubular or flat flowers; fixed 3-lobed labellum with a basal spur; erect or incurved lateral lobes; well-developed narrow midlobe; very short column without a foot and, 4 sessile free pollinia.
As currently interpreted the genus is polyphyletic, complex and clumsy. At least 5 natural groups can be recognised which would be better treated at generic rank.
Notes
The roots of Taeniophyllum species contain chlorophyll and are photosynthetic.
Nomenclature
Taeniophyllum Blume, Bijdr. 6: t.3, fig.70: 8: 355, t.70 (1825).
Type species: Taeniophyllum obtusum Blume.
Infrageneric Taxa: No infrageneric taxa are currently recognised.
References
Dockrill, A.W. (1967). Australasian Sarcanthinae. The Australasian Native Orchid Society, Sydney.
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.