Description from Flora of China
Arisanorchis Hayata; Gymnochilus Blume; Mariarisqueta Guinea.
Herbs, terrestrial or occasionally epiphytic, small. Rhizome decumbent, moniliform to terete, fleshy, with many contracted nodes; roots usually reduced to fine hairs and arranged along ridges on rhizome internodes, rarely fleshy and emerging from rhizome nodes. Stem erect, very short to elongate, glabrous, with 2 to several subrosulate or scattered cauline leaves. Leaves often withered at anthesis, ovate to cordate, with a short petiole-like base dilating into a tubular amplexicaul sheath. Inflorescence erect, terminal, racemose, very short to elongate, 1- to many flowered, glabrous to pubescent. Flowers resupinate, usually small, mostly not secund; ovary shortly pedicellate, twisted, fusiform, glabrous to pubescent. Sepals membranous, outer surface glabrous to pubescent, connate for half to almost entire length and forming a tube, or rarely free. Petals usually connivent with dorsal sepal; lip adnate to column margin at base, sometimes simple and entire though usually 3-partite; hypochile often dilated and saccate, containing fleshy, lobed or seriate (comblike) papillose calli; mesochile subtubular, short to elongate; epichile spreading, 2-lobed or rarely entire, margin laciniate, dentate, wavy, or entire. Column short, ventrally with 2 elongate armlike appendages (stelidia) parallel to rostellum; anther erect, ovoid, 2-locular; pollinia 2, each longitudinally 2-partite, granular-farinaceous, clavate, attached to solitary oblong viscidium; rostellum deeply bifid, 2 elongate arms erect, parallel; stigma lobes 2, separate, convex, rather large, placed laterally near apex of column and below rostellum. Capsule ellipsoid.
Hayata considered species with an entire lip to comprise a distinct genus, Arisanorchis, but they conform to Cheirostylis in other respects (sepals basally fused and forming a tube, column with two elongate stelidia, rostellum deeply bifid) and are most likely peloric forms. A monographic revision of the genus is highly desirable given that overlapping species concepts remain a problem in separating taxa named from different regions. The endemic species of Taiwan and Hong Kong in particular remain poorly known and are in need of re-examination.
About 50 species: from tropical Africa through tropical Asia to New Guinea, Australia, and the Pacific islands; 17 species (eight endemic) in China.
(Authors: Chen Xinqi (陈心启 Chen Sing-chi); Stephan W. Gale, Phillip J. Cribb, Paul Ormerod)