Acianthera hagsateri is similar to A. geminicaulina (Ames) Pridgeon & M.W.Chase, but differs in the small-sized plants, shorter ramicauls, smaller, succulent leaves, much shorter inflorescence born at the base of the leaves, dorsal sepal erect, linear-oblong, petals mucronate with margins strongly serrat-ed-lacerate, and by the entire, obovate lip.
Plant epiphytic, rhizomatous, small, to 5 cm tall. Rhizomes short, straight, the internodes up to 4.5 mm long. Roots filiform, greenish-white, some-times stained with purple, up to 0.7–0.8 mm in di-ameter. Ramicauls short, stout, 4–10 mm long, erect, terete, slightly thickened toward the apex, covered by two scarious, tubular sheaths when young. Leaf 32 × 12–13 mm, sessile, ascendant, succulent, green stained with reddish-purple or sometimes completely reddish-purple, elliptical to ovate, acute, apex mi-nutely 2-lobed, with a mucron between the lobes, margin entire, slightly convex on the adaxial surface, base cuneate. Inflorescence born from the apex of the stem, shorter than the leaf, racemose, 1- to 3-flow-ered, ca. 5 mm long without flowers, including the pinkish-purple peduncle 1.5 mm long. Ovary 1.5 mm long, purple, minutely echinate, the trichomes conic, articled to a stout pedicel, 2 mm long, microscopi-cally echinate. Floral bracts 3.5 mm long, obliquely funnel-shaped, long acute. Flowers relatively large in comparison with the plant size, to 2.4 cm in diam-eter, simultaneously-opening, bilabiate. Sepals palepurple, the nerves markedly pinkish-purple, membra-nous, minutely and sparsely verrucose on the abaxial surface, shortly hirsute, entire; the dorsal one 13.5 × 1.6 mm, linear-oblong, acute, shortly apiculate, slightly channeled, three-veined; the lateral ones con-nate into an ovate-lanceolate, obtuse, shortly apicu-late synsepal, 11.2 × 4.5 mm long, convex near the apex, concave toward the base, chordate at the base, 6-veined. Petals 4.7× 1.6 mm, translucent, mem-branaceous, slightly falcate, oblong-elliptical, acute, aristate, 3-veined, strongly serrate-lacerate along the margins, the margins, base, and nerves pinkish-purple. Lip 3.3 × 1.9 mm, similar in color to the se-pals, fleshy, entire, verrucose, thickened towards the base, oblong, subacute, shortly apiculate, truncate at the base, three-veined; the disc with a small pair of marginal, thickened, slightly erect calli, extended from the base up to near the apex, channeled among them. Column 2.6 mm long, pinkish-purple at the base, green pale at the apex, stout, slightly curved at the middle part, ventrally channeled, thickened at the base, clinandrium denticulate, with a basal extension to form a very short foot. Stigmatic cavity ventral, suborbicular; rostellum ventral, helmet-like. Anther ventral, yellow. Pollinarium not seen. Capsule ellip-soid, 1 cm long, with persistent perianth.