Nepenthes muluensis

Description

Nepenthes muluensis is a tropical pitcher plant endemic to Borneo. It grows in highland habitats at elevations of 1700 to 2400 m above sea level. Nepenthes muluensis is a climbing plant. The stem may attain a length of 4 m and is up to 5 mm in diameter. Internodes are cylindrical in cross section and up to 8 cm long. The leaves of this species are coriaceous and sessile. The lamina is lanceolate in shape and up to 8 cm long by 1.5 cm wide. It usually has an acute apex and is gradually attenuate towards the base, extending into an amplexicaul sheath. Up to 4 longitudinal veins are present on either side of the midrib. Pinnate veins are numerous but indistinct. Tendrils are up to 8 cm long. Rosette and lower pitchers are up to 7 cm high and 3 cm wide. They are ovate in the lower third, becoming cylindrical or conical above. The peristome is approximately cylindrical and up to 5 mm wide. Its inner margin is lined with small but distinct teeth. The pitcher mouth is round to ovate and has an oblique insertion. The lid or operculum is ovate and generally obtuse. It bears a number of filiform appendages (≤5 mm long) on its upper surface. Upper pitchers are cylindrical for the most part, often with a bulbous basal quarter. Like their lower counterparts, they are relatively small, reaching only 10 cm in height and 2 cm in width. They have a pair of ribs in place of wings. The waxy zone of the inner surface is well developed. The pitcher mouth is round and bears a cylindrical peristome up to 3 mm wide. The lid is orbicular and lacks appendages. An unbranched spur is inserted near the base of the lid. Nepenthes muluensis has a racemose inflorescence. It is very compact: the peduncle is only up to 3 cm long, while the attenuate rachis reaches 10 cm in length. Pedicels are up to 5 mm long and lack bracts. Sepals are ovate and up to 2 mm long. A study of 120 pollen samples taken from two herbarium specimens (J.H.Adam 2401 and J.H.Adam 2405) found the mean pollen diameter to be 32.0 μm (SE = 0.4; CV = 8.7%). The species completely lacks an indumentum, with all parts of the plant being glabrous. The type population of N. muluensis from Mount Mulu has a distinctive pitcher colouration. Lower pitchers are generally dark purple with sparse yellow speckles. The upper pitchers of this form are usually purple with numerous yellowish-white speckles. They often have a white peristome and lid. Plants from Mount Murud produce darker-coloured pitchers.