Cheiradenia Lindley (1853b: 1)

Thiago E. C. Meneguzzo, José F. A. Baumgratz & Cássio Van Den Berg, 2015, Taxonomic studies in the Aganisia complex (Orchidaceae, Zygopetalinae), Phytotaxa 238 (1), pp. 1-39 : 12

2. Cheiradenia Lindley (1853b: 1) .

Zygopetalum sect. Cheiradenia (Lindl.) Kuntze in von Post & Kuntze (1903: 602). Type: — Cheiradenia cuspidata Lindley (1853b: 1) .

Etymology:— From Greek, χειρ, hand αδένας, gland, in allusion to the lip callus.

Epiphytic herbs with sympodial growth, caespitose. Roots thick, spongy. Flowering pseudobulb inconspicuous, homoblastic, ovoid, orbicular in transverse section; cataphylls at the base, non-leafy, non-scarious, non-articulate. Leaves 2–3 per pseudobulb; petiole conduplicate, distinct from blade, margin non hyaline; blade articulate, conduplicate, narrowly oblong or oblanceolate, rarely narrowly obovate, base attenuate, apex apiculate, abaxial face with 1 prominent nerve. Inflorescences racemose, simple or double, axillary in inner cataphyll, taller than the plant, erect, pedunculate, rachis congested, blooming acropetally; bracts narrowly lanceolate, patent; bracteole apparently 1, lanceolate, longer than the ovary. Flowers resupinate, pedicellate. Dorsal sepal free but lateral ones adnate to the column foot, oblique. Petals free, obovate. Lip free, slightly trilobed, mobile, unguiculate, transversely oblong, strongly concave, lateral margins erect, apex truncate, blade with ¾ of distal portion with 1 longitudinal and conical callus, with free apex, distal portion free, apex 4-cuspidate. Column semi-terete, column foot shorter than column, apex with conspicuous triangular stigmatic wings; anther incumbent, clinandrium not projecting over the anther, margin entire, external face of anther cap entire, apex rounded, inner face bilocular face; pollinia 4, in 2 pairs, juxtaposed, ovoid, laterally compressed, unequal in size and shape, tegula and caudicle not seen, viscidium transversely rhombic; stigma transverse; rostellum unlobed, triangular, not exceeding the stigma, rostellum remnant unlobed, concave. Capsules ellipsoid, 6-carinate, smooth surface; seeds not seen.

Distribution and habitat:— This monospecific genus occurs in Trinidad and the Guiana Shield, high in canopy rainforests or riparian forests surrounded by savannahs, from sea level to 1,500 m. It is frequently described in herbarium specimens to be associated with thick moss layers. In Brazil it is found in biome Amazônia, vegetation type floresta de terra firme (dryland forest). TDWG code: 81 TRT-OO 82 FRG-OO GUY-OO SUR-OO VEN-OO 84 BZN-AP.

Diagnostic characters:— The genus is distinguished by its small size (plant up to 7 cm high), caespitose habit with inconspicuous pseudobulbs covered by non-leafy, non-articulate and non-scarious cataphylls, articulate plicate leaves, a petiole with non-hyaline margin, inflorescence slightly taller than the leaves, rachis congested, small flowers (sepals up to 0.3 cm long), lip entire with blade with ¾ of distal portion with 1 longitudinal and conical callus, with free apex, distal portion free, apex 4-cuspidate, and column with inconspicuous stigmatic wings.