Octarrhena Thw.,
Enum. Pl. Zeyl. (1861) 305
Small sympodial epiphytic or terrestrial plants. Stem elongated, not swollen, sometimes laterally compressed. Leaves c. 5 to many, arranged in two rows, sheathing at the base, glabrous, laterally compressed or filiform-terete, articulate or not, duplicate, stiffly thin-textured to carnose. Inflorescence lateral, a raceme or carrying a single flower, sometimes distinctly flattened or winged. Flowers small to very small, resupinate, often orange-brown, greenish, yellowish or whitish. Sepals connate at the base or nearly free. Petals free, almost always very much shorter than the sepals. Lip without spur, not mobile. Column-foot absent. Pollinia 4, or 8, solid-waxy, caudicles present or absent, stipe absent, viscidium present.
Distribution
Sri Lanka, South-east Asia, Malesia, east to Fiji. About 50 species; in New Guinea c. 40 species.
Habitat
Epiphytes in hill and montane forest, at high altitudes commonly terrestrial in ground moss.
Notes
Most species of this genus are very delicate moss-like plants with tiny flowers that are roughly triangular in shape, somewhat similar to those of the neotropical genus Stelis. Some of the larger species resemble members of the genus Oberonia, as they have similar laterally flattened leaves, but the lateral inflorescences immediately distinguish Octarrhena from Oberonia.
The number of pollinia is either 4 or 8. Those species with 8 pollinia may have all the pollinia of equal size, or they may have 4 relatively large and 4 very small pollinia. Those species with 4 pollinia comprise the former genus Chitonanthera.
A few species, in particular Octarrhena lorentzii J.J.Sm. and Octarrhena platyrhachis P.Royen, are noteworthy for the strongly flattened rachis of the inflorescence. This feature they have in common with some species of the genus Microtatorchis, an otherwise not closely related genus of monopodial orchids also found in New Guinea.
Species included on this CD-ROM:
Octarrhena angraecoides
Octarrhena angustifolia
Octarrhena angustissima
Octarrhena aporoides
Octarrhena aristata
Octarrhena bilabrata
Octarrhena brassii
Octarrhena calceiformis
Octarrhena cordata
Octarrhena cucullifera
Octarrhena cupulilabra
Octarrhena cylindrica
Octarrhena cymbiformis
Octarrhena exigua
Octarrhena falcifolia
Octarrhena filiformis
Octarrhena filiformis var. brachyphylla
Octarrhena filiformis var. glabra
Octarrhena firmula
Octarrhena gibbosa
Octarrhena goliathensis
Octarrhena gracilis
Octarrhena latipetala
Octarrhena lorentzii
Octarrhena macgregorii
Octarrhena miniata
Octarrhena montana
Octarrhena obovata
Octarrhena platyrhachis
Octarrhena podochiloides
Octarrhena purpureiocellata
Octarrhena reflexa
Octarrhena salmonea
Octarrhena spathulata
Octarrhena tenuis
Octarrhena teretifolia
Octarrhena torricellensis
Octarrhena trigona
Octarrhena umbellulata
Octarrhena vitellina
Octarrhena wariana