Synonyms: Hydrorchis D.L.Jones & M.A.Clem. APNI*
Description: Terrestrial herbs, sympodial; roots subterranean, filamentous; tuberoids paired and often produced on the tips of stolons.
Leaves well-developed, green, basal, 1 per shoot, cylindrical with a longitudinal furrow, hollow, not petiolate.
Inflorescence racemose or spicate, many-flowered, terminal, emerging through a slit in the furrow in the upper part of the leaf. Flowers resupinate. Dorsal sepal free, cucullate, slightly longer and much broader than lateral sepals. Lateral sepals free. Lateral petals free, slightly shorter and much narrower than dorsal sepal. Labellum free, attached at base of column; lamina not lobed or weakly 3- or 4-lobed, with crenulate to rugulose [or entire] and often undulate margins, with paired basal and sometimes single median and/or apical calli [or lacking calli]. Column lacking free filament and style, stubby; column wings fused to column, expansive in upper half, narrow to broad. Column foot absent. Anther erect, parallel to the axis of the column, persistent. Pollinia 4, granular. Stigma entire. Rostellum ventral.
Distribution and occurrence: World: 11 species, Australia, New Zealand, Polynesia, Indon., eastern Asia. Australia: 10 species(8 species endemic), all States except N.T.
Text by R. R. Rowe, key to species updated by Matt A.M. Renner (5 November 2020).
Taxon concept:
| | Key to the species | |
| 1 | Labellum long rectangular, 3–4 times longer than broad, 3–4 mm long and at least two-thirds as long as the slender, elongate ovary. Flowers widely spaced on inflorescence | 2 |
| Labellum short rectangular, or tapering, or (M. arenaria) broadening slightly toward apex, not long rectangular; 1–3.5 mm long and less than half as long as the turgid ovary. Flowers closely spaced on inflorescence | 3 |
| 2 | Labellum apical callus elliptic, domed, and prominent; overlapping the labellum margin at the apex of the labellum apical notch | Microtis rara |
| Labellum apical callus round to cordate; separated from the labellum margin, and not overlapping the labellum margin
Back to 1 | Microtis oblonga |
| 3 | Labellum margins entire, without bulging and protruding marginal cells; usually plane but in some individuals slightly undulate, | Microtis parviflora |
| Labellum margins crenulate, with bulging and protruding marginal cells; usually undulate in distal third, but not undulate in some individuals and less conspicuously undulate in M. arenaria
Back to 1 | 4 |
| 4 | Labellum deeply notched, lobes slightly splayed so that labellum broadens slightly toward the apex. Labellum apical callus in contact with the labellum margin at the apex of the labellum apical notch or close to it | Microtis arenaria |
| Labellum shallowly notched or not; labellum tapering slightly toward the apex or parallel-sided. Labellum apical callus not overlapping the labellum margin at the apex of the labellum apical notch, usually well-separated from the margin
Back to 3 | 5 |
| 5 | Labellum parallel-sided. Basal calli separated | Microtis unifolia |
| Labellum tapering toward apex. Basal calli fused
Back to 4 | Microtis angusii |
|
