- –Nepenthes rhombicaulis in The Heredity 26(10): 44. 1972, nom. nud., syn. sec. Cheek & Jebb 2001
- Type: Sumatra, near Prapat, G. Pangulubao, alt. 1700 – 1900 m, 29 Mar 1972, S. Kurata 4300 (Nippon Dental College)1
- Type: Sumatra, near Prapat, G. Pangulubao, alt. 1700 – 1900 m, 29 Mar 1972, S. Kurata 4300 (SING)
Terrestrial climber to 20 m tall. Climbing stem 4-angled, 5-10 mm diam.; short shoots and rosettes present. Leaves sessile, those of rosettes and short shoots scattered, lanceolate, several cm long; those of climbing shoots lanceolate, 12-22 by 3-4 cm, apex subpeltate to emarginate, the base clasping the stem by 1/2-2/3 its circumference, not decurrent or sheathing. Longitudinal nerves 2 or 3 on each side of the midrib in the outer 1/4 of the blade, innermost vein arising from 1/3-1/2 way along midrib. Pennate nerves oblique. Lower pitchers ventricose in the lower half, cylindrical in the upper part, 6-12 by 2.5-3.5 cm, with two fringed wings; mouth orbicular, oblique; peristome subcylindrical, 3-5 mm broad, ribs c. 0.5 mm apart, outer edge expanded and undulate, inner toothed; lid elliptic-oblong or ovate, 2.5 by 1.7-2.5 cm broad, apex rounded, base truncate, lower surface with an appendage near the apex, nectar glands bordered, c. 0.15 mm diam.; spur divided to the base with two filiform branches, c. 5 mm long. Upper pitchers unknown. Inflorescence 30-40 cm long; peduncle 15-20 cm long; partial peduncles 2-flowered, length unknown; bracts absent (not mentioned or figured in the protologue); pedicels 10-15 mm long; tepals elliptic, 4 by 3 mm; androphore 4 mm long. Fruits fusiform, valves lanceolate 20-25 by 5 mm. Indumentum of stem glabrous, with prominent glands; leaf margin reddish brown hairy; pitchers sparsely pubescent; lower surface of tepals, and fruit valves minutely pubescent. Colour of lower pitchers red or pale green with purple spots, peristome red.A
The description above is largely taken from the protologue. Nepenthes rhombicaulis is extremely poorly known although reported in the protologue as being ‘common’ on the mountains surrounding Lake Toba. Only the type collection exists. Subsequent purported field observations (
Hopkins et al. Carnivorous Plant Newsl. 19 (1990) 19-28 Schmid-Hollinger Carnivorous Plant Newsl. 23 (1994) 62-63 ) have not been supported by voucher specimens and their descriptions and photographs do not appear to match the type. The combination of a sharply 4-angled stem, absence of upper pitchers and presence of an apical appendage on the lower surface of the lower pitcher lid (not seen in the SING specimen) is unique: each are individually unusual characters within the genus.
N Sumatra: G. PangulubaoA
Subalpine forest; altitude unknown.A