Deciduous terrestrials with fleshy tubers and an erect stem on which flat or channelled smooth leaves are arranged in a rosette at the base or near the centre of the stem. The unbranched inflorescence carries white, green or yellowish stalked or sessile flowers in a terminal raceme. The dorsal sepal overlaps with the petals (which are not lobed) to form a hood over the column. The labellum, which has a basal spur, is unlobed or 3-lobed with the lobes short or long.
Significant Generic Characters
Deciduous autotrophic terrestrial orchids; tubers fleshy, subterranean; leaves few-many, flat or conduplicate, smooth, sheathing at the base, non-articulate, spiral, variably arranged on the stem; inflorescence racemose, terminal; flowers resupinate, mostly white, green or yellowish; dorsal sepal overlapping with the petals to form a galea; petals entire; labellum usually 3-lobed, with a nectariferous basal spur; pollinaria 2, each with a sectile pollinium on a caudicle and a naked viscidium; stigmata 2, the lobes reduced to sessile swellings fused to the base of the labellum.
Size and Distribution
A genus of about 75 species distributed in tropical parts of Asia, South-east Asia, Malaysia, Philippines, Indonesia, New Guinea, Polynesia and Australia where there are 3 species, all tropical, 2 endemic. State occurrence: Queensland.
Peristylus banfieldii and Peristylus candidus grow in open forest and on swamp margins in seasonally wet (monsoon season) soils and Peristylus chlorandrellus grows in well-drained soil in rainforest.
Pollination: The flowers of the native species of Peristylus are insect-pollinated but the vectors are unknown. They probably have similar relationships and pollination systems to species of Habenaria.
Reproduction: Reproduction in the native species of Peristylus is mainly from seed although the native species can also produce occasional daughter tubers. Seed dispersal takes 4-8 weeks from pollination and the capsules develop in an erect position. Apomixis is unknown in the genus.
Seasonal Growth: The native species of Peristylus occur in the tropics and their growth is closely tied in with the wet season. In Peristylus banfieldii and Peristylus candidus, the tubers sprout with the onset of the wet and the plants grow and flower during the wet season and die down with the onset of the dry. In Peristylus chlorandrellus the plants are above ground until about August and then become dormant.
Flowering: Peristylus banfieldii and Peristylus candidus flower between January and April, whereas Peristylus chlorandrellus flowers May to July.
Hybrids: Natural hybrids are unknown between the native species of Peristylus.
Fire: Peristylus banfieldii and Peristylus candidus grow in some habitats that are fire-prone whereas Peristylus chlorandrellus grows in rainforest.
The name Peristylus is derived from the Greek peri, around, and stylos, column, in reference to the column arms on each side of the column.
Perennial geophytic herbs, autotrophic, deciduous, sympodial. Plants glabrous. Flowering and non-flowering plants monomorphic. Tubers fleshy, subterranean, paired; replacement tuber formed on a short dropper; daughter tubers absent or on horizontal, fleshy, stolonoid roots. Roots filamentous, short to long, fleshy, unbranched. Stem erect, emergent, unbranched, fleshy or wiry. Trichomes absent. Leaves few-several per shoot, spirally arranged, scattered with the upper ones reduced in size and bract-like, sometimes forming a basal rosette or central rosette on the scape, flat or conduplicate, smooth, non-articulate, entire, sessile; base sheathing; lower leaves often reduced to imbricate, tubular sheathing bracts. Venation unknown. Inflorescence a terminal raceme, few-many-flowered. Peduncle similar to or longer than the rhachis. Rhachis similar to or shorter than the peduncle, straight. Floral bracts small to large. Pedicel short, merging with the ovary. Ovary straight or twisted, narrow. Flowers resupinate, often crowded, small, green, white or yellowish, lasting a few days, opening sequentially in a spiral. Perianth segments entire, narrow to relatively broad, persistent on the capsule. Dorsal sepal free, dissimilar or subsimilar to the lateral sepals, erect to incurved, cucullate, concave, overlapping with the petals to form a galea. Lateral sepals free, dissimilar to the dorsal sepal, porrect, deflexed or divergent. Petals free, overlapping with the dorsal sepal to form a galea. Labellum fixed to the basal margins of the column, markedly dissimilar in size and shape to the sepals and petals, calcarate. Labellum lamina unlobed or 3-lobed, often deeply so; lateral lobes small to large, narrow to broad, porrect to widely divergent; midlobe short to long, narrow to broad. Spur short to long, subglobose to cylindrical, straight or curved, often distally dilated. Callus obscure, or fleshy, in front of the opening to the spur. Nectar present. Column porrect from the end of the ovary, very short, lacking free filament and style. Column wings absent or present as sessile lateral appendages. Column foot absent. Pseudospur absent. Anther dorsal, erect or reclinate, fused basally with the column, 2-celled, erostrate, the cells extended at the base into arms which subtend the caudicles. Pollinaria 2. Pollinia 2, narrow, clavate, sectile, attached by long narrow caudicles at right angles to the pollinia. Viscidia 2, naked, terminal, oblong to ovate. Rostellum small, 3-lobed, situated between the anther arms and the stigmatophores. Stigma convex, 2-lobed, the arms (stigmaphores) sessile, convex or channelled, adnate to the labellum base and lateral appendages. Capsules dehiscent, glabrous, erect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Peristylus is sometimes included in Habenaria and the distinction between them is often not clear. The major differences lie in column structure which is a complex feature in the subtribe Habenariinae. In Habenaria the stigmatophores are stalked and not fused with the labellum base whereas in Peristylus the sessile stigmatophores are reduced and fused to the labellum base and column appendage.
Habenaria sect. Peristylus (Blume) Benth. in Benth. & Hook.f., Gen. Pl., 3: 625 (1883), orth. var.
Bateman, R. M., Hollingsworth, P.M., Preston, J., Yi-bo, L., Pridgeon, A.M. and Chase, M.W. (2001). Phylogenetics of Orchideae in Genera Orchidacearum. Volume 2, Orchidoideae (Part 1) 224-232, edited by A.M.Pridgeon, P.C.Cribb & M.W.Chase.
Cribb, P.C. (2001). Peristylus in Genera Orchidacearum. Volume 2, Orchidoideae (Part 1), pp. 341-343, edited by A.M.Pridgeon, P.C.Cribb & M.W.Chase.
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.
Seidenfaden, G. (1977). Peristylus Bl. Dansk Botanisk Arkiv 31: 27.