Electronic Flora of South Australia
Electronic Flora of South Australia
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Electronic Flora of South Australia genus Fact Sheet

Family: Orchidaceae

Citation: R. Br., Prod. Fl. Nov. Holl. 320 (1810).

Derivation: Greek mikros, small; otos, an ear.

Synonymy: Not Applicable

Common name: Onion-orchids.

Terrestrial glabrous herbs, arising annually from underground ovoid to spheroid tubers, often produced some distance from the parent plant; leaf solitary; sheath long; lamina elongate and terete, more or less hollow.

Raceme of few to many small resupinate flowers; floral bracts small, acute, hardly exceeding the short pedicels; perianth glabrous, usually green; dorsal sepal broad and cucullate, erect; lateral sepals almost equal in length but very much narrower, spreading or recurved, not connate; petals shorter than or nearly equal in length to the sepals, more or less erect, incurved or spreading; labellum sessile, about as long as the other perianth-segments, oblong to ovate or orbicular, truncate or emarginate, usually more or less pendulous or decurved against the ovary; calli if present usually paired at the base, median and single along the centre and near the tip, or the labellum quite smooth; column very short or relatively wide, semicylindrical, with membranous obtuse auricle-like wings, attached to about mid-anther level; anther terminal, erect, almost entirely above the stigma, more or less hemispherical, 2-celled; pollinia obscurely 2-lobed, pollen granular; caudicle often very short or absent; stigma broadly oval, slightly prominent; rostellum dark, its oval tip becoming detached, with a very short thread-like caudicle to which loosely coherent pollen masses adhere.

Distribution:  9 species occurring in Australia, mostly south of the tropics, 2 of which extend to New Zealand, New Caledonia, Indonesia, the Philippines, Taiwan, China and Japan.

Biology: Flowers of most Microtis are self pollinated if insects do not visit and many are apomictic as well. In some areas intermediate forms presumed to be hybrids can set up large clonal populations by apomixis and vegetative reproduction. (R. Bates (1984) J. Adelaide Bot. Gard. 7:45-89.)

Key to Species:
1. Labellum without callosities, entire; lateral sepals spreading, not recurved in mature flowers
2. Labellum ovate to elliptic; lateral sepals very blunt, not hidden by the labellum; flowers less than 2 mm diam
M. atrata 1.
2. Labellum orbicular; lateral sepals acute, hidden by the labellum; flowers greater than 2 mm diam
M. orbicularis 2.
1. Labellum with callosities; lateral sepals recurwed or revolute in mature flowers
3. Labellum apex acute or obtuse with a small downturned apiculus, margins slightly undulate or entire, callosities at the base but not at the apex
M. parviflora 3.
3. Labellum apex truncate, emarginate or 2-lobed, no downturned apiculus, margins crenulate, distinct callosities at the base and the apex
4. Flowers distant; labellum almost as long as the ovary; dorsal sepal shallowly concave below; petals spreading widely, not hidden
M. rara 4.
4. Flowers not distant; labellum less than half as long as the ovary; dorsal sepal deeply concave below; petals partly hidden within the dorsal sepal
M. unifolia 5.

Author: Not yet available

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