Cheirostylis ovata

Velvet Orchids

Deciduous terrestrials with thick, fleshy, irregularly ridged, above-ground creeping rhizomes that have no roots but are anchored by masses of fine root hairs.  The broad leaves, which arise in a basal rosette, are thin-textured, petiolate, light green and sometimes have a pale band along the midrib. Racemes short, terminal on a shoot, hairy. Flowers small, sometimes not opening freely, longer than wide, right-way-up, dull-coloured, sparsely hairy. Dorsal sepal and petals overlapping to form a hood. Lateral sepals fused together. Labellum attached to the anterior base of the column, with a narrow pouched base and a deeply bilobed apex with large, broad, toothed lobes. Basal pouch with narrow simple or branched calli. Column short, with 2 prominent curved apical arms.

Significant Generic Characters

Terrestrial orchids, deciduous; rhizomes succulent, above-ground, creeping with an erect apex, irregularly swollen at the internodes, constricted at the nodes, rootless, anchored by dense clusters of short white rhizoids; leaves petiolate, in a basal rosette, relatively broad, thin-textured, glabrous, light green, often with a pale median band; inflorescence racemose, short, terminal on a shoot; flowers resupinate, often short-lived, dull-coloured (green and white), externally hairy; sepals connate basally; dorsal sepal and petals overlapping to form a galea; lateral sepals fused to form a synsepalum. Labellum attached to the anterior base of the column; hypochile similar length to the epichile; epichile bilobed with 2 large dentate lobes. Basal pouch shallow, containing small elongate simple or branched calli. Column short, with 2 stigmas and 2 elongate arms (stylidia).

Size and Distribution

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distribution map

A genus of about 20 species distributed in tropical regions from Africa to Asia, South-east Asia, Polynesia and Australia where there are 2 endemic species. Cheirostylis ovata occurs in northeastern Queensland between Iron Range (1238 S) and Eungella and Cheirostylis notialis is found between Miriam Vale in southeastern Queensland and Grassy Head (3048 S) in northeastern New South Wales. State occurrence: Queensland, New South Wales.

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Ecology

The native species of Cheirostylis grow in sheltered positions in rainforest, vine thickets and wet sclerophyll forest. Cheirostylis ovata frequently grows among rocks; Cheirostylis notialis often in littoral forests. Plants of both species are dormant over late spring and early summer and become covered by fallen leaves and litter. The new shoots of the orchid grow up through this layer and the fine root hairs produced from the ventral swellings on the rhizome become attached to the decaying leaves, litter and rocks. Elevation ranges from sea level to 750 m alt.

Biology

Pollination: The flowers of Cheirostylis ovata may be insect-pollinated but those of Cheirostylis notialis are self-pollinating (Jones 1997).

Reproduction: Species of Cheirostylis reproduce solely from seed. Seed dispersal takes 3-4 months from pollination and the capsules develop in an erect position. There is no elongation of the peduncle or pedicels. Apomixis is unknown in the genus.

Seasonal Growth: Plants of Cheirostylis have leaves for 4-6 months and survive the dry parts of the year as leafless quiescent plants. During this time the plants become covered with fallen leaves and other forest litter, the new shoots growing up through this detritus.

Flowering: The native species of Cheirostylis flower between August and November.

Hybrids: The native species of Cheirostylis do not participate in natural hybridisation.

Fire: The native species of Cheirostylis do not grow in fire-prone habitats.

Derivation

Cheirostylis is derived  from the Greek, cheir, hand, stylis, style or column, an apparent reference to the protruding column arms.

Botanical Description

Perennial, deciduous, epiphytic, lithophytic or terrestrial herbs, sympodial. Roots absent, replaced by masses of filamentous rhizoids on the ventral side of the rhizome. Rhizome prostrate to decumbent, fleshy, irregularly swollen at the internodes, constricted at the nodes, unbranched, prostrate. Stem erect, abbreviated, fleshy, short, usually 1 shoot per plant. Pseudobulbs absent. Trichomes present on peduncle, rhachis, bracts, ovaries and the exterior of the sepals, unbranched, multiseriate, eglandular. Leaves lasting 1 season, often withered at anthesis, simple, few per shoot, petiolate, sheathing at the base, forming a loose rosette. Leaf lamina of similar length and width, thin, membranaceous, glabrous, flat, smooth, entire, light green, sometimes with a pale median band. Venation acrodromus to campylodromus, with cross-veinlets and few anastomoses. Inflorescence racemose, terminal on a growth, few-flowered, erect. Peduncle longer than the rhachis, hirsute, with sheathing hirsute sterile bracts.  Floral bracts sheathing, hirsute. Ovary elongate, asymmetric, straight or curved, hirsute. Flowers resupinate, not crowded, sometimes opening tardily, dull coloured (sepals green to reddish, petals and labellum white), hairy, pedicillate. Sepals connate basally. Dorsal sepal closely overlapping with the petals to form a galeaLateral sepals fused into a synsepalum. Petals of similar length to the sepals, asymmetric, forming a galea with the dorsal sepal, membranousLabellum fixed by its basal margins to the anterior basal margins of the column, immoveable, markedly dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina divided into a hypochile and an epichile; hypochile subequal in length to the epichile, channelled, with a pouched base containing 2 groups of elongate simple or branched calli-like glands; epichile sessile; lamina large, bilobed, with large spreading dentate to lacerate lobules. Nectar absent. Column lacking free filament and style, elongated, with 2 protruding parallel  stigmatic arms (stylidia) at the column apex. Column wings absent or vestigial. Column foot absent. Pseudospur absent. Anther dorsal, 2-celled, persistent, basifixed, with a short rostrum. Pollinarium present. Pollinia 2, clavate, deeply grooved, curved, yellow, sectile. Viscidium present or vestigial. Rostellum ventral, elongate, in 2 parts, closely paralleling the stylidia. Stigmas 2, situated at the base of the stylidia. Capsules dehiscent, hirsute, erect; peduncle not elongated in fruit; pedicels not elongated in fruit. Seeds numerous, light coloured, winged.

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Taxonomy

Within the Goodyerinae, Cheirostylis can be distinguished by rootless moniliform rhizomes attached to the strata by clumps of rhizoids, connate sepals, labellum base with simple or branched calli-like glands and column with 2 prominent arm-like stylidia.

Some authors (eg Ormerod and Cribb 2003), include Gymnochilus Blume and Arisanorchis Hayata in Cheirostylis based on gynostemium characters.  These genera are vegetatively dissimilar to Cheirostylis sens. strict. and molecular sequencing is needed to determine the true relationships within the group.

Nomenclature

Cheirostylis Blume, Bijdr. 6: t.1, f.1b; 8:413 (1825).  Type species: Cheirostylis montana Blume.

Infrageneric Taxa: No infrageneric taxa are recognised.

References

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. (1997). A taxonomic revision of Cheirostylis (Orchidaceae) in Australia. Muelleria 10: 75-83 (1997).

Ormerod, P. and Cribb, P (2003). Goodyerinae in Pridgeon, A.M.,