Acianthella is a small genus of tropical ground orchids previously included in Acianthus

Acianthus

Acianthus is a small genus of 9 species, 8 endemic in Australia and 1 in New Zealand, from the orchid family . Previously there were more species included in Acianthus, but about half of them have now been redistributed to other genuses, such as Acianthella.The name is derived from the Greek words...

but is now distinguished "by tiny green flowers on long thin ovaries, sepals of similar shape and size, lacking apical clubs, narrow petals and no basal glands on the labellum

Labellum

Labellum is the Latin diminutive of labium, meaning lip. These are anatomical terms used descriptively in biology, for example in Entomology and botany.-Botany:...

." There are about 7 species altogether, 2 endemic in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, and 5 in New Caledonia

New Caledonia

New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

. Both the Australian species are self-pollinating and very difficult to grow. It was described by David LLoyd Jones and Mark Alwin Clements in 2004. The type-species is Acianthella amplexicaulis.