Cheiradenia is a monotypic genus of epiphytic orchids in the family Orchidaceae (order Asparagales), placed in subtribe Zygopetalinae (tribe Cymbidieae, subfamily Epidendroideae). The genus was established by John Lindley in 1853 in Folia Orchidacea and contains a single species, Cheiradenia cuspidata.
These are miniature epiphytic plants with a short rhizome and caespitose growth habit, vegetatively resembling the smaller species of Cyclopogon. The pseudostem is formed by sheaths of distichous, membranous leaves with imbricate bases, the leaf surfaces smooth or lightly grooved. Inflorescences are racemose, erect, and longer than the leaves, terminating in a very short, spike-like rachis densely covered with bracts from which small, inconspicuous flowers barely protrude. The sepals and petals are flat and of equal length. The lip is somewhat clawed (unguiculate), articulated to the column foot, broad and slightly trilobed, bearing a distinctive transverse callus-like thickening that ends in finger-like projections — a feature reflected in the genus name. The column is short and thick, with a terminal anther containing two waxy pollinia.
The only species, C. cuspidata, is native to the northern Amazon basin, recorded from Venezuela, Guyana, Suriname, French Guiana, and northern Brazil. A later synonym, Cheiradenia imthurnii Cogn., was published in Flora Brasiliensis in 1906.
Etymology
The genus name Cheiradenia derives from the Greek words chira (χείρ, hand) and adenos (ἀδένος, gland), referring to the callus-like thickening of the flower lip that terminates in protrusions resembling fingers. The species epithet cuspidata is Latin for "with a rigid point."
Distribution
Cheiradenia cuspidata is native to the northern Amazon basin of South America, with records from Venezuela, Guyana, Suriname, French Guiana, and northern Brazil. It grows at elevations of approximately 200 to 700 metres in warm, humid tropical rainforest.
Ecology
This is an epiphytic orchid with caespitose (clumping) growth, found on moss-covered tree trunks and in humus-rich pockets within the warm, humid forests of the tropical northern Amazon. Its miniature size and inconspicuous flowers make it easily overlooked in the dense rainforest understory.
Taxonomy Notes
Cheiradenia was described by John Lindley in Folia Orchidacea (Cheiradenia 4) in 1853, with Cheiradenia cuspidata as the type and only accepted species. A synonym, Cheiradenia imthurnii, was proposed by Alfred Cogniaux and published in Martius's Flora Brasiliensis (vol. 3, part 6, p. 481) in 1906, but this is not currently accepted. GBIF's taxonomic record for the genus shows an empty authorship field. The genus is classified within subtribe Zygopetalinae (tribe Cymbidieae, subfamily Epidendroideae) of Orchidaceae.
