Alternative names: Not Applicable

Description:
Perennial, rarely annual, herbs terrestrial, epiphytic or growing on rocks; arising from creeping rhizomes, annually renewed tuber or thickened rootstocks usually functioning as storage organs; aerial stem often swollen at the base into a pseudo-bulb, and often with adventitious or aerial roots; leaves parallel-veined or curviveined, entire, often distichous; the base of the leaf sheathing or not; in saprophytic species the leaves usually reduced to bracts or scales.

Flowers bisexual, zygomorphic, very rarely regular, in spikes, racemes or panicles, or solitary; perianth mostly petaloid, of 6 segments in 2 whorls, free or variously connate, occasionally joined to form a tube; the 3 outer segments called sepals; the 2 lateral inner ones called petals; the third petal (except in Thelymitra) modified to form the labellum which often differs greatly in size and shape and often bears outgrowths--calli, hairs, fringes or other appendages; nectary sometimes contained within a spur or sac from one or more of the perianth-segments; anther and stigma borne on a more or less erect usually fleshy structure (column), a prolongation of the floral axis; anthers 1 or 2, 2-locular, introrse, opening by longitudinal slits; pollen grains rarely free, usually aggregated in tetrads or larger groups (pollinia) that are mealy, waxy or quite hard and sometimes terminating in a sterile caudicle; stigma borne in the part of the column facing the labellum, of 2 or 3 lobes, the median lobe sometimes represented by a small process (rostellum) extruding between the stigma and anther; viscid areas sometimes associated with the rostellum and to these the pollinia become attached either directly or by a connecting strip of non-viscid rostellar or columnar tissue known as the stipe; ovary inferior, l-celled with 3 parietal placentae, rarely 3-celled.

Fruit a capsule, usually dehiscing by 3 or 6 longitudinal slits; seeds numerous and very minute, often elongated, without endosperm or a differentiated embryo.

Distribution:  Worldwide; the largest family in the world, with 500-800 genera and perhaps 30,000 species. At least 80 genera occur in Australia. Epiphytic species are very abundant in the tropics but not represented in S.Aust.

Biology: If the axis of the inflorescence is erect, the labellum is on the upper (adaxial) side in the young bud, but the pedicel usually twists as the bud develops, so that the labellum comes to be on the lower side. The term resupinate is used for any orchid flower that has the labellum on the lower side. Occasional peloric flowers occur (that is flowers in which the labellum is modified to resemble the other petals). For further on the putative hybrids reported here see Bates (1985) Checklist of Australian terrestrial orchid hybrids.

Taxonomic notes: The following were found particularly useful in the preparation of this treatment: Clements, M. A. (1982) Preliminary checklist of Australian Orchidaceae;, George, A. S. (1971) A checklist of the Orchidaceae of Western Australia, Nuytsia 1:166-196; Moore, L. B. & Edgar, E. (1970) Flora of New Zealand, vol. 2; Nicholls, W. H. (1969) Orchids of Australia (most S.Aust. species); Rupp, H. M. R. (1969) The orchids of New South Wales, facsimile edition with supplement by D. J. McGillivray; Willis, J. H. (1970) A handbook to plants in Victoria, edn 2, vol. 1.

Key to Genera:

1. Leaves scale-like at flowering (plants saprophytic); flowers pendent and pedicellate, bell-like
2. Perianth-segments pink, free, spreading from the base	DIPODIUM 9.
2. Perianth-segments brown and white, fused to form a tube	GASTRODIA 12.
1. Leaves usually with well developed laminae at flowering; flowers various
3. Flowers not resupinate, so that the labellum lies above the column; perianth-segments free
4. Leaves several, basal (ovate-elliptic); labellum c. 15 mm long or more, much longer and broader than all the other perianth-segments	CRYPTOSTYLIS 7.
4. Leaf 1; labellum less than 15 mm long, shorter than some other perianth-segments
5. Leaf linear-terete, sheathing much of the scape; flowers almost sessile; perianth-segments often small; labellum longer than the column	PRASOPHYLLUM 19.
5. Leaf linear or linear-lanceolate, shortly sheathing the scape, reddish; flowers on a distinct pedicel; labellum shorter than the column
6. Leaf linear-lanceolate; labellum surface smooth	CALEANA 3.
6. Leaf narrow-linear; labellum surface tuberculate	PARACALEANA 18.
3. Flowers resupinate on the scape, labellum always below the column; perianth-segments various
7. Leaves 2 to several, basal and/or cauline
8. Labellum lamina 3-lobed, (e.g. fig. 963 D); lateral sepals narrow-linear; leaves linear
9. Flowers brightly coloured (yellow, purple or whitish), on slender pedicels; petals more than 13 mm long, clawed, conspicuous	DIURIS 10.
9. Flowers greenish or brownish, almost sessile; petals less than 6 mm long, not clawed, hidden by an erect dorsal sepal	ORTHOCERAS 17.
8. Labellum lamina not lobed
10. Flowers numerous, close-set in a spiral around the scape; perianth-segments pink or white, 4-5 mm long; labellum margin fringed; column not winged	SPIRANTHES 21.
10. Flowers 1 to several, loosely spaced in the raceme; perianth-segments green or reddish, more than 5 mm long; labellum margin smooth; column winged
11. Flowers solitary; perianth-segments free, radially spreading; labellum relatively large with dark waxy calli; leaves 2, basal	CHILOGLOTTIS 5.
11. Flowers 1 to several, conspicuously hood-shaped; the hood or galea consisting of the cohering dorsal sepal and petals; labellum relatively small and mobile, with a basal appendage, without calli; leaves more than 2, basal and/or cauline	PTEROSTYLIS 20.
7. Leaf at flowering basal and single (except 1 or 2 in Leporella)
12. Leaf pubescent; floral bracts small, not longer than the ovaries; labellum often on a movable claw; column broadly winged
13. Labellum with calli; flowers 1 to several, variously coloured	CALADENIA 2.
13. Labellum without calli; flowers 1 or 2, purple	GLOSSODIA 13.
12. Leaf glabrous
14. Leaf at least twice as long as wide; perianth various
15. Flowers almost actinomorphic; labellum not differentiated; column variously ornamented with hair-tufts or papillate lobes	THELYMITRA 22.
15. Flower zygomorphic, with a well differentiated labellum; column not ornamented
16. Leaf narrow-lanceolate, not terete nor tubular; labellum 8-28 mm long, densely covered with brown to reddish-purple hairs (rarely glabrous); bracts sometimes leaf-like	CALOCHILUS 4.
16. Leaf terete, tubular, sheathing; labellum 1-5 mm long, with I or 2 calli or smooth; bracts minute. MICROTIS 16
14. Leaf as wide or nearly as wide as long; perianth zygomorphic
17. Stem or scape shorter than the flower at flowering; leaf basal; flower solitary, relatively large and hoodshaped by an incurved dorsal sepal; labellum enlarged, immobile	CORYBAS 6.
17. Stem or scape 1 to several times longer than the flower; flowers several
18. Labellum undivided, margins entire, glabrous; leaf and lateral sepals various
19. Leaf lanceolate and oblique to the stem; labellum with 2-4 rows of calli; petals erect, glandular distally	CALADENIA 2.
19. Leaf orbicular or wide-cordate, at a right angle to the stem; labellum with 2 basal calli; petals not erect
20. Leaf petiolate and raised above ground, red beneath; labellum fleshy, acutely 3-angular; column not winged	ACIANTHUS 1.
20. Leaf sessile on the ground, green beneath; labellum membranous, oblong, subacute; column winged	CYRTOSTYLIS 8.
18. Labellum divided or fringed, toothed or pubescent (e.g. fig. 962B.); leaf ovate; lateral sepals deflexed
21. Labellum straight, lamina wider than long, not lobed, with a radiating reddish-purple fringe, without papillae or calli; petals glandular	LEPORELLA 14.
21. Labellum recurred, lamina longer than wide, with papillae or calli; petals not glandular
22. Lateral sepals much longer than all other segments, white or pink; labellum margin entire; lamina glandular-villous; leaf hardly developed at flowering; plant not drying black	ERIOCHILUS 11.
22. Lateral sepals and petals similar, maroon; labellum 3-lobed, the middle-lobe fringed; lamina with sessile calli; leaf present at flowering; plant drying black	LYPERANTHUS 15.

Author: Prepared by J. Z. Weber and R. Bates