Scientific name: Cleisostoma dorsisacculatum Aver.English name: Vietnamese name: Lan miệng kín dạng gốiOther name:
Perennial monopodial epiphytic herb. Stem simple or basally few branched, rigid, ascending to erect, (8)15–25(35) cm long, (3.5)4–5(5.5) mm in diam., with few wiry, straight or flexuose roots branching at apex; internodes (0.6)1–2(2.4) cm long. Leaves sessile, dorsiventral, leathery, straight or slightly recurved, oblong lanceolate, (6)8–12(14) cm long, (1.4)1.6–2(2.2) cm wide, unequally bilobed, with oblong, apically rounded lobes. Inflorescence lateral panicle (12)15–30(35) cm long, scape and rachis grassy green; scape (10)12–15(18) cm long horizontal or ascending, often curved or slightly flexuose, with 2–4 short, broad, light pale gray-brownish sterile bracts, with (4)5–12(14) branches (1)2–10(12) cm long, raceme rachis straight to slightly flexuose, branch rachides almost straight, with many spirally arranged, lax flowers distant on (1)2–4(5) mm. Floral bracts minute, triangular, acute, about 1 mm long and wide. Pedicel and ovary (4)4.5–5.5(6) mm long and (0.6)0.7– 0.9(1) mm in diam., light green to dull olive, sometime hardly hairy with sparse very small rusty trichomes, usually S-curved, abruptly broadening at the base. Flowers widely opening, (6)6.5–7(7.5) mm across; sepals and petals rather fleshy, very sparsely hairy with very small rusty trichomes, spreading, later turned back, brown, sometime with 1 indistinct brown-yellowish longitudinal strip and dull yellowish along the margin; lip white, with purple apex of side lobes; column white, sometime with light purple tint, apically at sides with dark purple spots; anther cap white with light yellow tint; pollinia yellow. Sepals oblong obovate, concave, cucullate, blunt to rounded at apex, (3.2)3.4–3.6(3.8) mm long, (2)2.2(2.4) mm wide, lateral sepals slightly oblique. Petals oblong broadly lanceolate, blunt, as long as sepals, (0.8)0.9–1.1(1.2) mm wide, slightly oblique. Lip spurred, (4.2)4.5–4.8(5) mm long (from spur apex to the upper side of side lobes), 3-lobed; side lobes narrowly triangular, truncate, parallel and forward protruding, (1.1)1.2–1.4(1.5) mm long, 0.5–0.6 mm wide at the base, each side lobe at the base (on upper margin) with small enrolled fold and prominent broadly conic papillose boss placed near the middle on internal surface; median lobe fleshy triangular to obscurely sagittate, (1.2)1.4–1.5(1.6) mm long, (1.6)1.8–2(2.2) mm wide, blunt to roundish or subtruncate, straight, forward directed or slightly upright, finely irregularly rough, disc with 2 papillose inflations separated by median furrow ending proximally by small hairy boss continuing into the spur in form of high almost glabrous keel (incomplete septum); spur ovoid, saccate, vertically down directed, at the apex sometime slightly back curved, flattened, dorsally strongly concave, (2.8)3–3.2(3.4) mm long, (2)2.2–2.4(2.6) wide with entire, round apex and incomplete longitudinal septum inside. Back-wall callus in form of large, flattened, pillow-like, half-ovoid, finely papillose container 2–2.2 mm long, 1.6–1.8 mm wide, swelling during anthesis and sometimes opening with age at apex by two narrow lateral splits. Column short, broad, (1.6)1.8–2(2.2) mm high, 2.4–2.5(2.6) mm wide, with large, forward directed subquadrate arms of rostellum supporting at apices viscidium lobes; stigma concave, transversely oblong with adaxial margin in form of fleshy shortly conoid swelling. Anther cap hemispherical, 0.9–1 mm broad, elliptic viscidia. Pollinia 2, each deeply split into 2 with elongate, apically bifid beak. Stipe (tegula) 0.8– 1 mm long, in form of plate, flat at the base, conduplicate folded and bent at apex, in flat part attached to viscidium; viscidium saddle-shaped with two parallel narrowly subequal hemispheric portions, 0.35–0.45 mm in diam. Fruits unknown.
Species name refers unusual pillow-like container placed on the spur back-wall, unique among its congeners.
Habitat, phenology and conservation status
Canopy epiphyte. Primary and secondary broad-leaved evergreen forests on silicate rocks. 800–1200 m. Fl. October–December.
Estimated IUCN Red List status – DD.
Vietnam province: Lam Dong (Bao Loc)