Starfish Orchids
Leafless epiphytes (rarely with a few small leaves, non-Australian) with widely spreading flat warty greenish roots and a very short stem. Inflorescences are long, thin, unbranched with small, round flowers that only last a few hours and are produced in spasms. The labellum, which is hinged to the apex of the column foot, has large lateral lobes and a fleshy midlobe with a narrow central hollow and a hairy finger-like callus. The column is short with a relatively long column foot that is attached at right angles to the column. The anther has 2 unusual thread-like side appendages.
Similar Genera
Significant Generic Characters
Epiphytic/lithophytic orchids, usually leafless; roots flat, verrucose, green, photosynthetic; stems very short; leaves absent (rarely a few small leaves present, non-Australian); inflorescence racemose; flowers small, numerous, lasting a few hours, opening in spasms; perianth segments thin-textured, imbricate; sepals and petals subsimilar; labellum hinged to the apex of the column foot; lamina 3-lobed, without a spur; lateral lobes large, erect; midlobe well-developed, fleshy, with a central hollow, resembling a spur; callus finger-like, hairy; column short, with a long foot at right angles to the column; pollinia 4, sessile on a stipe, in 2 appressed unequal pairs.
Size and Distribution
A small genus of 3 species, 1 each in India, Indonesia and Australia. The Australian species, Chiloschista phyllorhiza, is distributed in the northern parts of the Northern Territory, including Bathurst Island, some Torres Strait islands and between Cape York (about 17º16' S) and the Tully River (about 10º40' S) in northern Queensland. State occurrence: Queensland (including Moa and Thursday Islands), Northern Territory.
Ecology
Chiloschista phyllorhiza grows on trees and rocks in rainforest, streamside vegetation, swamps, moist gullies and gorges. It also often grows on mangroves.
Biology
Pollination: The flowers of Chiloschista phyllorhiza last 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 Chiloschista phyllorhiza 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 Chiloschista phyllorhiza grow mainly during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Chiloschista phyllorhiza flowers in spring and early summer.
Hybrids: Natural hybrids involving Chiloschista phyllorhiza are unknown.
Derivation
Chiloschista, which is derived from the Greek cheilos, lip and schistos, cleft, refers to bilobed labellum of the type species.
Botanical Description
Perennial, leafless (rarely a few small leaves), epiphytic or lithophytic herbs, monopodial. Roots broad, flat in cross-section, verrucose, greenish, photosynthetic, adherent. Plants unbranched. Stem very short, fibrous. Pseudobulbs absent. Trichomes present on the labellum callus. Leaves absent, rarely a few small leaves present (non-Australian). Venation unknown. Inflorescence lateral, racemose, arcuate, multiflowered. Peduncle shorter or similar to the rhachis, thin, wiry. Rhachis thin, straight or flexuose. Floral bracts small, scarious, sheathing the base of the pedicel. Pedicel short, thin, merging with the ovary. Ovary short, straight. Flowers resupinate, small, stalked, opening in spasms along the rhachis, lasting a few hours (sometimes opening briefly the next day), white or yellowish, fragrant. Perianth segments thin-textured, short, broad, imbricate, spreading. Dorsal sepal free, subsimilar to the lateral sepals. Lateral sepals subsimilar to the dorsal sepal, attached to the column foot. Petals free or attached to the column foot, subsimilar to the sepals. Labellum hinged to the apex of the column foot, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina 3-lobed; lateral lobes large, erect; midlobe well-developed, calceiform, with a narrow central hollow, broad, blunt, the distal wall greatly thickened. Spur absent (labellum midlobe sometimes interpreted as a spur). Callus central, digitiform, 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 right angles to the column. Pseudospur absent. Anther terminal, incumbent, 2-celled, persistent, smooth, with a short rostrum, bearing 2 filiform, glandular or eglandular lateral appendages. Pollinarium present. Pollinia 4 in 2 appressed pairs, unequal, orange, hard, waxy, sessile. Stipe long, relatively broad. Viscidium broad, at an angle to the stipe. Rostellum large, decurved, deeply bifid. Stigma entire, deeply concave. Capsules dehiscent, glabrous, porrect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Within the Vandeae, Chiloschista is characterised by spreading flat verrucose green roots; very short stem; absence of leaves; hinged, 3-lobed labellum without a spur; fugacious flowers with short, broad imbricate tepals; large erect lateral lobes; well-developed calceiform midlobe with a narrow central hollow and thickened distal wall; digitiform hairy callus; short column with a long foot at right angles to the column and, 4 sessile pollinia in 2 unequal pairs.
Notes
The flattened roots of Chiloschista phyllorhiza contain chlorophyll and are photosynthetic.
Nomenclature
Chiloschista Lindley in Edwards’s, Bot. Reg. 18: sub.t. 1522 (1832).
Type species: Epidendrum usneoides D.Don. [Chiloschista usneoides (D.Don.) Lindl.].
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.