Caleana

Caleana, commonly known as duck orchids, is a genus of flowering plants in the orchid family, Orchidaceae that is found in Australia and New Zealand. The Australian species are found in all states but have not been recorded in the Northern Territory. Duck orchids have a single leaf and one or a few, dull-coloured, inconspicuous flowers. Most species are found in Western Australia but one species (C. major) occurs in eastern Australia and one (C. minor) occurs in eastern Australia and New Zealand. Orchids in this genus as well as the hammer orchids (Drakaea) are pollinated by male thynnid wasps. thumb|225px|Labelled diagram of Caleana nigrita

==Description== Orchids in the genus Caleana are terrestrial, perennial, deciduous, sympodial herbs usually with a few inconspicuous, fine roots and a dark red, oval-shaped, tuber. Replacement tubers called "droppers" form at the end of long root-like stolons. A single linear to egg-shaped leaf long develops near the base of the plant during the growing season and withers late in the flowering season. The leaf is folded lengthwise and often has purple markings. The flowering stem is wiry, dull brownish maroon and bears one to a few flowers each on a stalk long, each with a small leaf-like bract. The flowers are non-resupinate and glabrous. The dorsal sepal and the two lateral petals are similar in size and are narrow linear in shape with pointed or club-shaped ends. The dorsal sepal points downwards and is pressed against the column. The lateral sepals and two petals usually spread obliquely downwards and sideways. The dorsal sepal and petals are attached to the base of the column where it joins to the ovary. As is usual in orchids, one petal is highly modified as the central labellum. Duck orchids have an unusual, insect-like labellum which is attached to the rest of the flower by a sensitive stalk which holds the labellum above the flower in the "set" position. The labellum is attached to the column by a flexible "claw" which bends under the weight of a pollinating wasp. The column has broad wings and when the labellum is touched, it rapidly turns down, trapping a visiting insect between the labellum and column wings so that the insect comes into contact with the sexual parts of the column. The labellum is flask-shaped, narrowing near the end with the narrow end covered with small raised calli or glands which are usually black, but may be maroon or greenish. In some species the calli may cover a greater part, or even all of the labellum (as in P. minor). Glands on the labellum emit pheromones which are sexual attractants for male thynnid wasps. Flowering occurs in spring in most species and is followed by the fruit which is a non-fleshy, dehiscent capsule containing up to 500 seeds.