Phoringopsis dockrillii

Truffle Orchids

Deciduous terrestrial orchids that reproduce from seed and also form clonal colonies. Fertile and sterile plants are monomorphic. Sterile plants consist solely of 1-2 erect leaves. Fertile plants consist of a multiflowered inflorescence produced as the leaves develop and arising from the base of a leaf. Flowers right-way-up and dull-coloured (usually greenish). Perianth segments free and inconspicuous. The dorsal sepal is held close to the column and the lateral sepals and petals reflex back against the ovary, leaving the labellum exposed. Labellum hinged at the end of a short column foot. The labellum itself is unlobed and reduced to a simple oblong structure, but it is dominated by a large insect-like callus which has a swollen fungus-like base and a free extended neck which is ornamented with long glands. Column elongate, incurved, with 2 unequal pairs of projecting wings, the upper pair smaller and extending above the anther.

Similar Genera

Arthrochilus

Significant Generic Characters

Terrestrial orchids; plants monomorphic; leaves 1 or 2, basal, erect, much longer than wide; racemes multiflowered; flowers small, resupinate, greenish; sepals and petals inconspicuous; lateral sepals and petals reflexed; tepal bases and column foot smooth, non-papillate; labellum lamina simple, oblong, without a peltately attached supporting stalk; callus insectiform, dominating the labellum, with a swollen fungus-like base and a free extended neck ornamented with long, penicillate, basally-attached, clubbed glands, these glands also present on the basal part of the callus where it is fused to the lamina; composite labellum structure hinged to the centre of the column foot; column with 2 unequal pairs of projecting column wings and a foot; pollinia deeply bilobed, not attached to a viscidium. The genus is distinguished from Arthrochilus by its different leaf arrangement, resupinate flowers, smooth tepal bases, labellum hinge attached in the centre of the column foot, labellum lacking a peltately attached supporting stalk and the strongly swollen fungiform callus ornamented with long, thin penicillate glands.

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Size and Distribution

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A genus of 3-4 species distributed disjunctly in northern Australia and southeastern Papua New Guinea. In Queensland the genus occurs on some islands of Torres Strait and on the mainland it is distributed between Cape York (1041' S) and Kurrimine Beach (1746' S). The genus also occurs in Kakadu National Park in the Northern Territory and on the Mitchell Plateau in the Kimberley Region of Western Australia. State occurrence: Queensland (including Thursday Island), Northern Territory, Western Australia.

Ecology

Species of Phoringopsis grow in well-drained or seasonally wet soils in woodland, heathland and rocky sites. A common habitat on Cape York Peninsula is known locally as "Epacrid scrub" because of the dominance of tall species of Leucopogon. In parts of the Northern Territory and Western Australia members of the genus also grow close to or among tussocks of spinifex grass. Soils are usually sandy or coarse gravels. The emergence and growth of these orchids is closely tied in with the rains of the monsoonal wet season.

Biology

Pollination: No pollination study has been carried out on this genus but the floral syndrome is very similar to that of Arthrochilus and these orchids are probably pollinated by male thynnine wasps in a relationship involving pseudocopulation.

Reproduction: Species of Phoringopsis reproduce vegetatively to form clonal colonies and spread by the production of daughter tubers on the end of stolonoid roots. Seeds are dispersed within 6-10 weeks of pollination.

Seasonal Growth: In Phoringopsis the emergence of plants and subsequent growth is closely tied in with the rains of the monsoonal wet season. The leaves emerge after the first heavy soaking rains, usually in December-January, and are fully developed before flowering occurs. Plants die back after the rains finish and the dry season sets in, usually March-April. The most southerly species, Phoringopsis dockrilli, is exceptional in the genus with plants still being above ground in August-September.

Flowering: Most species of Phoringopsis grow and flower over summer (January-March) but the most southerly species, Phoringopsis dockrillii, can flower as late as August.

Hybrids: Species of Phoringopsis are not known to participate in natural hybridisation.

Fire: Fires are frequent in the areas where these orchids grow but any effects of the burns on the orchids are unknown.

Derivation

The generic name Phoringopsis, which is derived from the Greek phoringes, truffle, and -opsis, resemblance, refers to the fungus-like base of the labellum callus.

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Botanical Description

Perennial geophytic herbs, sympodial. Plants glabrous. Roots both filamentous and stolonoid. Tubers present, ovoid, solitary, fleshy, naked; replacement tubers absent; daughter tubers formed on the end of slender stolonoid roots. Stem erect, short, unbranched, with a membranous cataphyll at the apical node. Flowering and non-flowering plants vegetatively monomorphicTrichomes absent. Leaves 1 or 2, basal, unequal, subtending the inflorescence, distichous, sessile. Leaf lamina erect, much longer than wide, hypostomatic, convolute in bud; margins entire. Venation anastomosing. Inflorescence racemose, few-many-flowered, erect, terminal. Peduncle wiry, with a single sterile bract. Floral bracts reduced, semi-sheathing. Ovary elongate, ribbed, glabrous. Flowers resupinate, dull coloured (mostly greenish), subsessile. Perianth segments glabrous. Dorsal sepal free, smaller than the lateral sepals, erect. Lateral sepals mostly free, anteriorly decurrent on the column foot, larger than the dorsal sepal, reflexed against the ovary. Petals free, narrower than the sepals, reflexed against the ovary. Labellum free, hinged to the centre of the column foot by a short claw, strongly insectiform or fungiform, held erect, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina simple, unlobed, reduced, oblong-ligulate, base thickened; margins entire. Callus dominating the labellum, proximally swollen and fused to the lamina, distally free and elongated into a neck, ornamented with long, penicillate clavate calli, these calli also present on the basal part of the callus where it is fused to the lamina. Nectar absent. Spur absent. Column lacking free filament and style, elongate, incurved. Column foot short, with an apical bump. Pseudospur absent. Column wings fused to the column, with 2 pairs of elongate, incurved, unequal, wing-like projections, the larger pair situated medially, the smaller pair projecting over the anther. Anther terminal, 4-celled, persistent, basifixed, porrect. Pollinarium absent. Pollinia 4, clavate, flat, mealy, yellow. Viscidium absent. Rostellum ventral. Stigma entire, transverse, concave. Capsules dehiscent, glabrous, erect; sepals and petals persistent on the developing fruit; pedicels not elongating in fruit; peduncle not elongating in fruit. Seeds numerous, light coloured, winged.

Taxonomy

Phoringopsis is a segregate genus from Arthrochilus (Jones et al. 2002). It is distinguished by 1-2 elongate, distichous basal leaves, inflorescence emerging with the leaves, smooth, non-papillate column foot and sepal bases, labellum attached basally (not via a peltate stalk), and the callus fungiform and ornamented with penicillate calli.

A new species, P. lavarackiana, was described in 2004 (Jones and Clements 2004).

Nomenclature

Phoringopsis D.L.Jones and M.A.Clem., Orchadian 13(10): 457 (2002).

Type species: Phoringopsis byrnesii (Blaxell) D.L.Jones and M.A.Clem. [Arthrochilus byrnesii Blaxell].

Infrageneric Taxa: No infrageneric taxa are recognised.

References

Jones, D.L., Clements, M.A., Sharma, I.K., Mackenzie, A.M. and Molloy, B.P.J. (2002). Nomenclatural notes arising from studies into the tribe Diurideae (Orchidaceae). Orchadian 13(10): 437-468.

Jones, D.L. and Clements, M.A. (2004). Miscellaneous new species, new genera, reinstated genera and new combinations in Australian Orchidaceae. Orchadian 13(10): 457

Lavarack, P.S. (1975). Arthrochilus dockrillii: a new species of orchid from north Queensland. Proc. Roy. Soc. Qld 100: 100-103.

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