Distribution: Sabah, Borneo. Eastern slope of Mount Tambuyukon and Mount Kinabalu: Marai Parai plateau, Mesilau East River near Mesilau Cave, Upper Kolopis River. Latin description: Folia mediocria petiolata, lamina oblonga v. lanceolata, apice peltata, nervis longitudinalibus utrinque 4-5 ; ascidia rosularum ignota ; ascidia inferiora et superiora maxima, urceolata, alis 2 subfimbriatis, ore maximo obliquo ; peristomio in collum breve elongato, expanso, 10-30 mm lato, costis 1/2-2 distantibus, dentibus 2-4 x longioribus quam latis ; operculo maximo ovato-cordato, facie inferiore prope basin carina valida exaltata ; inflorescentia racemus magnus pedicellis inferioribus c. 20-25 mm longis 2-floris, superioribus brevioribus 1-floris ; indumentum parcum, villosum v. villoso-tomentosum.
Botanical description: Stem: generally prostrate or decumbent; not climbing, coarse, 15-30 mm thick, ≤6 m long (usually ≤3 m), yellow to green in colour, internodes ≤20 cm, cylindrical. Leaves: coriaceous, shortly petiolate, yellow to green in colour, with a wavy outer margin. Lamina oblong-lanceolate, 25-80 cm long and 10-15 cm wide, rounded and peltate at the apex, rounded at the base, abruptly attenuate towards the petiole. Tendril inserted 2-5 cm below the leaf apex. Petiole canaliculate, winged, ≤15 cm long, ≤1 cm thick, dilated at the base, with a sheath that clasps the stem for 3/4 of the circumference. Longitudinal veins 3-4 (rarely 5) on each side, originating from the basal part of the midrib, running parallel in the outer half of the lamina, pennate veins running obliquely towards the margin, irregularly reticulate in the outer part of the lamina. Tendrils about as long as the lamina, ≤50 cm long, 5-6 mm thick near the lamina, 10-25 mm thick near the pitcher, curved downwards, yellow to red in colour, darker near the pitcher. Pitchers: urceolate to short-ellipsoidal, 20-40 cm high, 11-18 cm wide, red to purple on the outside, inside surfaces lime green to purple in colour, with two fimbriate wings running almost from the base to the mouth, broader and more fimbriate towards the top, 6-25 mm wide under the mouth, the fringe segments ≤7 mm long, 2-4 mm apart. Glandular region covers the entire inner surface of the pitcher, about 300-800 glands/cm2, the glands in the lower part (digestive zone) not overarched, large such that the interspaces only form polygons, overarched in the upper half (conductive/retentive zone). Mouth horizontal to oblique, the front side of the pitcher 1/2 to 2/5 of the back side in length, elongated towards the lid into a neck 2.5-4 cm long. Peristome greatly expanded, 10-15 mm wide at the front side, 20-50 mm wide towards the lid, distinctly scalloped, prolongated at the interior side into a perpendicular lamina that is 10-20 mm wide, the ribs 0.5-1 mm apart at the inner side, 1-2 mm apart at the outer margin, teeth distinct, those of the interior margin 2 to 4 times as long as broad. Lid ovate to oblong, rounded at the apex, cordate at the base, 15-25 cm long, 11-20 cm wide, vaulted with a distinct keel running down the centre, midrib keeled in the basal half below, keel 5-10 mm high at some distance from the base, 3-8 mm wide, no appendages. Lower surface of the lid covered in many elevated glands, those on the keel with a wide mouth, the others with a very narrow one. Spur ≤20 mm long, unbranched, ascending from the back rib of the pitcher close to the lid, about 2 mm thick at the base, attenuate. Intermediate and upper pitchers rarely produced, conical, smaller, lighter in colour; usually yellow, wings reduced to ribs. Male inflorescence: a long raceme, peduncle 20-40 cm long, about 10 mm thick at the base, about 7 mm at the top, cylindrical, yellow-green to orange in colour, the rachis 30-80 cm long, angular and grooved, gradually attenuate. Lower partial peduncles 20-25 mm long, two-flowered, upper ones gradually shorter, one-flowered, all without bract. Flowers brownish-yellow in colour, give off strong sugary smell. Tepals elliptic to oblong, ≤8 mm long, obtuse, burgundy in colour. Staminal column 3-4 mm long, anthers in 1 of 1 1/2 whorls. Female inflorescence: generally like male inflorescence, but the tepals are somewhat narrower. Fruits short-pedicelled, 10-20 mm long, relatively thick, slightly attenuate towards both ends, orange-brown in colour, the valves 2.5-4 mm wide. Seeds filiform, 3-8 mm long, nucleus only slightly wrinkled, if at all. Indumentum: all parts of the plant covered with long, caducous, white or brown hairs when young, mature plants virtually glabrous. Stem with long spreading brown hairs when young, later glabrous. Pitchers densely covered with long spreading brown hairs when young, later sparsely hairy or glabrous. Inflorescences densely covered with adpressed brown hairs when young, later more sparsely hairy in the lower part, indumentum persistent in the upper part on the peduncles and on the perigone, ovaries densely appressedly hairy, fruits less densely hairy to glabrous. Other: colour of herbarium specimens dark-brown in varying hues.
Publications: Transact. Linn. Soc., XXII, p. 421 t. LXXII (1859) ; MIQ., Ill., p. 8 (1870) ; HOOK. F., in D.C., Prodr., XVII, p. 95 (1873) ; MAST., Gard. Chron., 1881, 2, p. 492 (1881) ; BURB., Gard. Chron., 1882, 1, p. 56 (1882) ; REG., Gartenfl., XXXII, p. 213, ic. p. 214 (1883) ; BECC., Mal., III, p. 3 & 8 (1886) ; WUNSCHM., in ENGL. & PRANTL, Nat. Pflanzenfam., III, 2, p. 260 (1891) ; STAPF, Transact. Linn. Soc., ser. 2, bot., IV, p. 217 (1894) ; BECK, Wien. Ill. Gartenz., 1895, p. 142, ic. 1 (1895) ; MOTT., Dict., III, p. 451 (1896) ; VEITCH, Journ. Roy. Hort. Soc., XXI, p. 234 (1897) ; BOERL., Handl., III, 1, p. 54 (1900) ; HEMSL., Bot. Mag., t. 8017 (1905) ; Gard. Chron., 1905, 2, p. 241 (1905) ; MACF., in ENGL., Pflanzenr., IV, 111, p. 46 (1908) ; in BAIL., Cycl., IV, p. 2129, ic. 2462, 3 (1919) ; MERR., Bibl. Enum. Born., p. 284 (1921) ; DANS., Trop. Nat., XVI, p. 202, ic. 7 (1927).
Diagrams: Transact. Linn. Soc., XXII, t. LXXII (1859) optima ; Gard. Chron., 1881, 2, p. 493 (1881) bona, asc. 1 ; Gartenfl., 1883, p. 214 (1883) bona, asc. 1 ; Wien. Ill. Gartenfl., 1895, p. 143, ic. 1 (1895) asc. 1 ; Journ. Roy. Hort. Soc., XXI, p. 228 (1897) optima ; Bot. Mag., t. 8017 (1905) optima ; BAIL., Cycl., IV, ic. 2462, 3 (1919) asc. 1 ; Trop. Nat., XVI, p. 203 (1927) asc. 1.
Collections: North Borneo. Mt. Kinabalu, IX 1913, Herbarium of the Sarawak Museum (material without flowers or fruits) ; Marai-parai Spur, 1-4 XII 1915, Clemens 11073, Herbarium Bogoriense, the Herbarium of the Buitenzorg Botanic Gardens (male and female material) ; 1650 m, 1892, Haviland 1812/1852, Herbarium of the Sarawak Museum (male and female material).
Sequenced nucleotides and proteins:
- Nepenthes rajah translocated tRNA-Lys (trnK) pseudogene (DQ007139)
- Nepenthes rajah trnK gene (AF315880)
- Nepenthes rajah trnK gene (AF315879)
- Nepenthes rajah maturase K (AAK56010)
- Nepenthes rajah maturase K (AAK56011)
Invalid: Nepenthes rajah auct. non Hook.f.: Slack, A. (Insect Eating Plants & How To Grow Them (1986)).
Synonym of Nepenthes × alisaputrana Adam & Wilcock (1992) [=Nepenthes rajah (Hook.f.) × Nepenthes burbidgeae (Hook.f.)].