Protologue: Fl. Brit. Ind. 6 (1893): 516
Amorphophallus bintangensis Ipor, Tawan & Meekiong: Amorphophallus loerzingii Alderw.; Amorphophallus panomensis Gagnep.
Tuber depressed-globose, 4-25 cm in diam., 2.5-15 cm high, dark brown outside, orangeish inside, rootscars annuliform thickened, tuber multiplying by gradual off setting or splitting. Leaf solitary, occasionally paired. Petiole smooth, rarely slightly rugulose at the base, 10-210 cm long, 0.5-10 cm in diam. at base, soft or rather turgid, background colour variable, whitish, greenish or reddish brown, mottled with numerous small, blackish green spots and large, circular or oval, creamy white spots, often confluent and internally with small blackish green spots or with a reddish-brown central, sometimes nearly entirely covering the surface, the base often with a bluish-purple hue. Lamina 10-250 cm in diam., rachises winged nearly to the base. Leaflets elongate elliptic, long acuminate, base long decurrent, 5-28 cm long, 1.5-10 cm in diam. Inflorescence solitary, short peduncled. Peduncle as for petiole but much shorter and sometimes paler, 3-20(-35) cm long, 0.8-6 cm in diam. (base), lengthening strongly in fruit. Spathe campanulate, broadly ovate or circular when spread, slightly longer than broad to slightly broader than long., 10-25(-40) cm long, 10-25(-40) cm in diam., base strongly convolute, shallowly constricted at the top. Limb obliquely erect during female anthesis, strongly reflexing just prior to male anthesis, or more rarely during or shortly after male anthesis, top obtuse or acute, margin often irregularly undulate, base outside yellowish green with whitish spots and streaks or with a purplish hue and whitish spots or very pale pinkish white with small, dark green, punctiform spots and large, rounded, whitish spots, margin pinkish, inside dark maroon, limb outside yellowish green, or bright pale green with whitish spots, the margin without spots and flushed with purple, inside pale yellowish white with bright green stripes along the margin or the latter entirely bright green with some faint whitish spots on the dorsal side, base of spathe within densely clothed with small, shortly ridge-like warts, this part producing a fair amount of fluid during female anthesis and that is being collected in the spathe base. Spadix in small specimens shorter than spathe, otherwise longer, 9-35(-55) cm long, shortly stipitate, stipe c. 1 cm long. Female zone cylindric or conic, 2-8 cm long, 1-3 cm in diam. Male zone cylindric or fusiform
(small specimens) to strongly obconic (largest specimens), 2-4 cm long, 1.2-3.5 cm in diam.; flowers congested. Appendix variable, 1.5-25(-30) cm long, 1-5(-25) cm in diam., rarely subglobose (small specimens), usually broadly ovate-fusiform and laterally compressed with or without a few longitudinal folds, or occasionally with a dense pattern of interconnecting, shallow grooves and raised areas in between, the upper third (or less) often quite abruptly narrowed and tapering to the acute, obtuse, occasionally strongly truncate (in very large specimens) or knob-like apex, the base sometimes stipe-like, the basal half in large specimens clearly inflated, often with staminodes intermediate between stamens and appendix wall and some longitudinal furrows, white, creamy white, or pale sulphur-yellow, sometimes with a pinkish hue, heating up considerably at opening of the spathe and during female anthesis and emitting a heavy, gaseous smell, inside holding a watery liquid after anthesis. Ovaries depressed, rarely subglobose, stipitate, circular in cross-section, basal half whitish, upper half pale or dark maroon, 2-3 mm in diam., 1-2 mm high, two-locular, one basal ovule per locule, stipe c. 0.7 mm long. Style distinct, 0.5-2 mm long, 0.8-1.2 mm in diam., creamy white, yellowish or maroon. Stigma large, capitate, oval in cross-section, obtriangular to cordate in lateral view, distinctly two-lobed, occasionally three-lobed, rarely only shallowly lobed, diam. 1 (base) -3.5 (top), 1.2-3 mm high, lobes obtuse, surface minutely scabrate or minutely rugose, pale lemon yellow, bright pale yellow, pale green or creamy white, becoming quite paler at male anthesis. Male flowers consisting of 3-5 stamens. Filaments 0.1-0.2 mm long, free. Anthers 2-3.2 mm long, 1-1.2 mm in diam., creamy white, quadrangular, polygonal or slightly elongate in cross-section, truncate, connective massive, pores subapical, sometimes lower part of adjacent anthers connate. Berries red or orange-red, elongate, 1.7-1.9 cm long, 1-2-seeded, often germinating in berry.
Distribution: Found in Indonesia (Sumatera, East Kalimantan), southern Thailand and Malay Peninsula.
The species occurs mostly in lowland forests and in open as well as in rocky places, at 0-850 m altitude.
Amorphophallus prainii is variable in the dimension of parts of the inflorescence. This is due to the conditions of the soils, in which the tubers grow. The appendix varies from nearly globose in small plants, through fusiform, to strongly inflated in large plants. The species is easily recognised by the sessile, campanulate, white spathe.