Acriopsis Reinw. ex Blume,
Bijdr. (1825) 376
Sympodial epiphytes. Rhizome short, creeping, branched, the few internodes between the pseudobulbs short with some early eroding, amplexicaul, acute scales. Main roots stiff, fleshy, branched, bearing many thin, ascending, acute, extensively branched catch-roots. Pseudobulbs crowded, consisting of more than one internode, (1--)2--3(--4)-leaved, ovoid, shallowly sulcate; lowest internodes bearing thin, silvery papyraceous, acuminate to cuspidate scales clasping the entire pseudobulb, upper internodes bearing fully developed leaves. Leaves articulate with the sheath, conduplicate when young; sheath clasping the pseudobulb; leaf blade oblong or linear, stiff herbaceous to subcoriaceous, multinerved; midrib sunken above, prominent below, the other nerves in fresh material not prominent. Inflorescence a raceme or a panicle, usually many-flowered, heteranthous, developing from the base of a pseudobulb on a short, rooting innovation with some amplexicaul, overlapping, ± triangular, acute scales. Peduncle relatively long, terete; internodes few, nodes with an amplexicaul, triangular, acute, membranous scale. Rachis ± straight; branches if present in the axil of a bract which resembles the peduncle scales. Floral bracts persistent, small, triangular, acute, membranous. Flowers small, resupinate, ± spirally arranged and irregularly spaced, widely open, cruciform. Pedicel slender, terete. Ovary slender, slightly conical, at a slight angle with the pedicel. Sepals lanceolate, boat-shaped, apex curved to the front; the lateral sepals completely fused to form a synsepal. Petals spreading, oblong to obovate, about as long as the sepals or slightly shorter. Lip trilobed, pandurate or entire; hypochile basally with the margins adnate to the lower half of the column, forming a tube which is open in front, inside with a laterally adnate, ± decurved outgrowth forming an oblique plate with a small opening on the side of the hypochilium; front part of the hypochile free, narrower than the epichile; epichile glabrous or slightly pubescent, bearing two short flattened keels which are centrally connate. Column ± straight or slightly S-curved, semi-orbicular in section, near the apex with two long, parallel, porrect or decurved long stelidia with ± swollen, translucent tips. Stigma between the stelidia ± narrowly elliptical in outline, flattened or with slightly elevated margins; rostellum beak-like or narrowly triangular, bifurcate, projecting above the stelidia. Anther two-locular, ± pear-shaped, covered by the large, hood-like margin of the clinandrium. Pollinia 4, connate in two pairs, the inner two often shorter and narrower, caudicles absent, stipe narrow, attached to a small viscidium. Fruit globose to ellipsoid to obovoid, opening with 3 valves, inside with elaters, the column and often the perianth parts persistent. Seeds ± fusiform, c. 0.1 mm long, tips acute; embryo surrounded by a wing of inflated cells.
(after Minderhoud and de Vogel, 1986, modified)
Sikkim, Burma, Thailand, Laos, Cambodia, Vietnam, Malay Peninsula, all over Indonesia, the Philippines, New Guinea, Palau Islands, Solomon Islands, Louisiade Islands, and Australia, 6 species. In New Guinea one, non-endemic, species [Acriopsis liliifolia (Koenig) Ormerod].
Epiphytes in primary and secondary forest, coastal swamp forest, on trees in savannahs, sometimes recorded growing in ants' nests in trees; altitude 0 to 1700 m.
An isolated genus, with slender inflorescences carrying inconspicuous small flowers, in which the lateral sepals are completely fused (as in Paphiopedilum). Rarely cultivated, but rather common in the wild.