Kaurorchis evasa

A small genus with only 1 species occuring in Australia, only growing in mist and cloud forests. This epiphytic orchid is anchored by filamentous roots that arise from the nodes on the rhizome. Kaurochis have small single-noded pseudobulbs, closely appressed to the rhizome and difficult to see. Each pseudobulb has a single terminal fleshy elliptic leaf with a notched apex. The inflorescence which arises from the nodes along the rhizome has a small head like dense cluster of pink flowers on the end of a peduncle which is 4 to 10 cm long. Each individual flower is approximately 0.3 cm wide, the petals are smaller than the sepals and the obscurely 3-lobed labellum is hinged to the apex of the column foot. Kaurochis flowers sporadically during spring and summer and occurs in tropical Queensland.

Significant Generic Characters

Epiphytic/lithophytic orchids; plants appressed; roots filamentous, from rhizome nodes; rhizomes long-creeping, brittle, branched; pseudobulbs almost vestigial, single-noded, widely spaced, closely appressed to the rhizome; leaf single, about as wide as long, thick and fleshy; inflorescence arising from rhizome nodes; peduncle widening near the apex; flowers densely crowded, relatively small; perianth segments thin-textured, glabrous; petals smaller than the sepals; labellum hinged to the apex of the column foot; labellum lamina very obscurely three-lobed, fleshy, densely papillate.

Size and Distribution

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distribution map

A small genus of 8-10 species distributed mainly in New Guinea and Indonesia  but with at least 2 species in India. A single species, Kaurorchis evasa, is endemic in northeastern Queensland between the Big Tableland south of Cooktown (1540' S) and Mt Halifax near Townsville (1910' S). State occurrence: Queensland.

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Ecology

Kaurorchis evasa grows on trees or rocks in mist and cloud forests above about 800 m alt. It is common on slopes and ridges where clouds, mists and fogs are frequent. The climate is tropical with the majority of rain falling during the summer wet season (December to March), with the remaining months much drier and having sporadic or intermittent rain.

Biology

Pollination: The flowers of Kaurorchis evasa last a few days and are pollinated by small flies that feed on nectar produced by the labellum.

Reproduction: Reproduction in Kaurorchis is solely from seed but details of capsule development and seed dispersal are unknown. Apomixis is unknown in the genus.

Seasonal Growth: The plants grow during the warmer months, particularly during the wet season, and are relatively quiescent for the remainder of the year.

Flowering: Flowering occurs sporadically during spring and summer.

Hybrids: Natural hybrids involving Kaurorchis are unknown.

Derivation

The generic name Kaurorchis is derived from the Greek kauros, brittle and Orchis, another genus of orchid but also a general term applied to orchids. The rhizomes are extremely brittle.

Botanical Description

Perennial, evergreen, epiphytic or lithophytic herbs, sympodial. Plants glabrous. Roots filamentous, produced from nodes along the rhizomes. Rhizomes closely appressed to the host, prominent, stout, long-creeping, branched, brittle, covered by closely sheathing, imbricate, scarious bracts. Pseudobulbs closely appressed to the rhizome, alternate, widely spaced, single-noded, oblong, covered by bracts and difficult to discern. Leaves subsessile, 1- per shoot, terminal on a pseudobulb, not sheathing at the base, flat, about as wide as long, smooth, thick and fleshy, coriaceous; apex unequally emarginate. Inflorescence arising from a stem node, multiple-flowered, erect or nodding at the apex. Peduncle well-developed, with 2-3 closely sheathing, imbricate or spreading, scarious sterile bracts.  Floral bracts large, not sheathing, spreading. Pedicel absent. Ovary short, straight, smooth. Flowers resupinate, sessile, lasting a few days, pinkish to purplish-red. Perianth segments thin-textured, not widely spreading. Dorsal sepal free, subsimilar to the lateral sepals, hooded; apex entire, flat.  Lateral sepals attached by their bases to the column foot; apex entire, flat. Petals free, porrect, dissimilar to the sepals; margins entire; apex entire, flat. Labellum hinged by a short claw to the apex of the column foot, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina more or less ovoid, very obscurely three-lobed, thick and fleshy, curved; lateral lobes small, basal, suberect; margins entire; apex nearly truncate. Callus obscure, consisting of a basal channel. Nectar present. Column small, lacking free filament and style, short. Column wings present, ventral and with prominent linear-tapered apical stelidia. Column foot well developed. Anther terminal, incumbent, 2-celled, persistent, basifixed, smooth, erostrate. Pollinarium absent. Pollinia 4 in 2 pairs, triangular, orange, hard, waxy. Viscidium absent. Rostellum ventral, transverse. Stigma entire, transverse, concave. Capsules not seen. Seeds numerous, light coloured, winged.

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Taxonomy

Kaurorchis, previously included within Bulbophyllum, was recently described as a segregate genus (Clements and Jones 2002). It was misspelt in the original publication (as Karorchis) but the orthographic error was later corrected (Jones and Clements 2004). It is distinguished from Bulbophyllum by its appressed, creeping brittle rhizomes, minute pseudobulbs, single fleshy leaf, capitulate inflorescence and densely papillate labellum.

Nomenclature

Kaurorchis D.L. Jones and M.A.Clem., Orchadian 13(11): 499 (2002). Type species: Kaurorchis evasa (T.E.Hunt and Rupp) M.A.Clem. and D.L.Jones.

References

Clements, M.A. and 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.

Jones, D.L. and Clements, M.A. (2004). Miscellaneous new species, new genera, reinstated genera and new combinations in Australian Orchidaceae. Orchadian 14(8): Scientific Supplement xv.

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.