Bulbophyllum quadrangulare J.J.Sm., Bull. Jard. Bot. Buitenzorg, sér. 2, 2 (1911) 16
Type: Bogor cult. (Branderhorst) s.n. (upper Digoel) (holo BO; iso L [all probably, no loc, no coll.])
Rhizome long creeping, thin, entirely covered with tubular sheaths. Pseudobulbs c. 2-3.5 cm apart, obliquely erect, ovoid, quadrangular, longitudinally grooved, c. 1.2-1.7 by 0.7-1.13 cm; 1-leaved. Leaf subovate-lanceolate, acute, apiculate, coriaceous, c. 3.75-4.9 by 1.5-1.8 cm; base shortly contracted in a petiole; midrib above grooved. Inflorescences 1-flowered, erect, exceeding the leaves in length; peduncle filiform, c. 11.3 cm long, in the basal part with a few small, tubular peduncle-scales. Floral bract tubular, 0.38 cm long. Flower rather large, c. 4.5 cm long. Median sepal erect, linear, acute, concave, 5(-7)-nerved, c. 2.4 by 0.35 cm; margins incurved. Lateral sepals deflexed, parallel, linear, acute, slightly falcate, c. 9-nerved, c. 2.7 by 0.48 cm; apex narrowed. Petals very small, parallel to the column, broadly oblong, falcate, obtuse, undulate, 1-nerved, 0.3 by 0.18 cm; upper margin erose except at the base; lower margin lacerate, proximally with a rather large lacerate lobule; apex acute, erose. Lip strongly mobile, in outline oblong, at a third above the base recurved, slightly 3-lobed, fleshy; base below the place of insertion bilobed, with retrorse lobes, 0.4 cm long; lateral lobes erect, somewhat retrorse, separated by a deep furrow in between; mid-lobe somewhat spathulate-obovate, distally suborbicular-dilated, rounded, proximally convex underneath, upper side convex, rugose, with a short longitudinal rib, underneath concave; apex broadly rounded, slightly more than 0.2 cm wide. Column 0.17 cm long; below the stigma with a callus; stigma deeply concave, ovate; stelidia distinctly exceeding the anther, subulate, slightly falcate; column-foot making an obtuse angle with the ovary, strongly incurved, when not flattened 0.18 cm long, distally strongly dilated and with a widely patent conical lobule on either side, its apex free. Anther cucullate, c. 0-06 cm long; connective strongly crested, its apex elongated and conduplicate. Ovary 6-grooved, 0.3 cm long; pedicel filiform, c. 1.3 cm long, articulate 0.33 cm above the base. (After Smith, 1913)
Colours: Rhizome initially green purple Pseudobulbs shiny pale green, in front more or less purple. Leaf above shining, underneath opaque pale green. Peduncle pale green tinged dirty violet. Median sepal pale yellowish; base pale yellow. Lateral sepals, splendidly golden yellow, to the apex paler. Petals hyaline, with few irregular dark purple spots and apex. Lip yellow, underneath dark purple-punctate, apex on either side dark purple. Column pale green; column-foot in the basal part pale green, the rest white, dark purple-punctate. Anther pale yellow; connective pale green. Ovary green, keels dirty violet.
Habitat: Epiphyte in lowland forest; 50-900 m.
Flowering time in the wild: April, May, July, August.
Distribution: Malesia (New Guinea).
Distribution in New Guinea: Papua (Indonesia); Papua New Guinea; see map 96-1521M.jpg.
Cultivation: Warm growing epiphyte.