Raspy Root Orchid
Coarse epiphytes with flat warty roots, a projecting fibrous stem and broad, spreading stiff papery leaves. Inflorescences are long, thin, unbranched with numerous, large, spidery orange flowers that usually only last a few hours. They have a small labellum that is hinged to the apex of the column foot. The column is short with a relatively long column foot that is attached at a sharp angle to the column.
Similar Genera
Significant Generic Characters
Epiphytic/lithophytic orchids; roots flat, verrucose/scabrous; plants moderately large; stems thick, fibrous; leaves large, stiffly papyraceous, in 2 ranks, longer than wide; inflorescence racemose; flowers small, numerous, lasting a few hours; perianth segments thin-textured, filamentous; sepals and petals subsimilar; labellum relatively small, hinged to the apex of the column foot; lamina 3-lobed, without a spur; lateral lobes large, erect, incurved distally and overlapping; midlobe well-developed, hollow, resembling a spur; column short, with a long foot at a sharp angle to the column; pollinia 4, sessile on a stipe, in 2 subequal pairs.
Size and Distribution
A monospecific genus with the single species, Rhinerrhiza divitiflora, endemic in eastern Australia and distributed between the Atherton Tableland (about 17º16' S) and the Hunter River (about 32º56' S) in northern New South Wales. In temperate and subtropical regions the plants are mainly found at low to moderate altitudes but in the tropics they are restricted to moderate or high altitudes in the ranges and tablelands. State occurrence: Queensland, New South Wales.
Ecology
Rhinerrhiza divitifloragrows on shrubs, trees and rocks in rainforest, wet sclerophyll forest, streamside vegetation, humid areas of open forest, moist gullies and gorges.
Biology
Pollination: The flowers of Rhinerrhiza divitifloralast a few hours and are produced in spasms, usually all the plants in an area flowering simultaneously. They are probably pollinated by native bees.
Reproduction: Reproduction in Rhinerrhiza divitiflorais 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 Rhinerrhiza divitifloragrow mainly during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Rhinerrhiza divitifloraflowers in spring.
Hybrids: Natural hybrids involving Rhinerrhiza divitifloraare unknown.
Derivation
Rhinerrhiza, which is derived from the Greek rhinein, file, rasp and rhizos, root, refers to the rough warty roots.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs, monopodial. Roots broad, flat in cross-section, verrucose /scabrous, adherent. Plants unbranched, moderately large, porrect. Stem short, relatively thick, fibrous. Pseudobulbs absent. Trichomes absent. Leaves lasting several seasons, crowded, distichous, spreading, sessile, longer than wide, mostly flat, thinly coriaceous, harsh, papyraceous; base sheathing the stem, persistent after leaf abscission, imbricate; margins undulate; apex uncinate, unequally emarginate. Venation unknown. Inflorescence lateral, racemose, arcuate to pendulous, multiflowered. Peduncle much shorter than the rhachis, thin, wiry. Rhachis straight. Floral bracts scarious, sheathing the base of the pedicel. Pedicel short, thin, merging with the ovary. Ovary short, straight. Flowers resupinate, relatively large, stalked, opening in spasms along the rhachis, lasting a few hours (sometimes opening briefly the next day), orange with red markings and a white labellum, fragrant. Perianth segments narrow, filamentous, thin-textured, incurved to spreading. Dorsal sepal free, subsimilar to the lateral sepals. Lateral sepals free, subsimilar to the dorsal sepal. Petals free, subsimilar to the sepals. Labellum hinged to the apex of the column foot, relatively small, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina 3-lobed, held forward of the column; lateral lobes large, erect, incurved distally and overlapping; midlobe well-developed, calceiform, hollow, broad, blunt, with a small apical lobule. Spur absent. Callus central, fleshy, 3-lobed, the bases of the marginal lobes attached to the bases of the labellum lateral lobes. Nectar unknown. Column short, at an angle to the apex of the ovary, lacking free filament and style, fleshy. Column wings vestigial or absent. Column foot long, at a sharp angle to the column. Pseudospur absent. Anther terminal, incumbent, 2-celled, persistent, smooth, with a short rostrum. Pollinarium present. Pollinia 4 in 2 appressed pairs, subequal, orange, hard, waxy, sessile. Stipe short, relatively broad. Viscidium broad, at an angle to the stipe. Rostellum short, decurved, deeply bifid. Stigma large, entire, concave. Capsules dehiscent, glabrous, porrect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Within the Vandeae, Rhinerrhiza is characterised by flat verrucose/scabrous roots; harsh, papyraceous leaves; hinged, relatively small, 3-lobed labellum without a spur; fugacious flowers with long filamentous tepals; large lateral lobes with distally incurved imbricate margins; well-developed hollow calceiform midlobe; 3-lobed callus; short column with a long sharply angled foot and, 4 sessile pollinia in 2 subequal pairs.
Nomenclature
Rhinerrhiza Rupp, Victorian Naturalist. 67: 206 (1951).
Type species: Sarcochilus divitiflora Benth. [Rhinerrhiza divitiflorus (Benth.) Rupp].
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.