Nepenthes inermis

Nepenthes inermis


Nepenthes inermis Danser in Bull. Jard. Bot. Buitenzorg, sér. 3, 9: 312, f. 10. 1928 sec. Cheek & Jebb 2001
    • Lectotype: Sumatra, G. Kerinci, alt. 1800 m, 26 Apr 1920, Bünnemeijer 9695 (BO)
  • "Nepenthes bongso" sensu Tamin & Hotta 1986: 83 partim, f. 2 toto2, non Korth., p.p., err. sec. Cheek & Jebb 20011
  • 1. Cheek, M. R. & Jebb, M. H. P. 2001: Flora Malesiana - Nepenthaceae, Series I, Volume 15. – Leiden: Nationaal Herbarium Nederland, Universiteit Leiden branch, 2. Tamin, R. & Hotta, M. 1986 – In: Hotta, M., Diversity and Dynamics of Plant Life in Sumatra. – Kyoto: Sumatra Nature Study (Botany), Kyoto University

Other sources

Jebb, M. H. P. & Cheek, M. R. 1997: A skeletal revision of Nepenthes. – Blumea 42(1): 1-106: 52


Canopy epiphyte, climbing to at least 45 cm tall. Stems terete to rounded triangular, (2-)3-5 mm diam., internodes of climbing stems 3.5-5.5(-9.5) cm, axillary buds inconspicuous. Leaves thinly coriaceous, sessile, those of short stems and rosettes unknown, those of climbing stems oblanceolate-spathulate to oblong, (5-)6.5-8(-12) by 1-1.6(-2.5) cm, apex rounded-acute, margin slightly revolute, base attenuate, clasping the stem for half its circumference, not auriculate or decurrent. Longitudinal nerves 2 or 3 on each side of the midrib in the outer half from the leaf base, fairly conspicuous. Pennate nerves numerous, reticulate. Lower pitchers unknown. Upper pitchers originating gradually or abruptly from the end of the tendril, incurved with a 1-2 cm arc, infundibuliform 5.5(-9) cm long, lower 1/2-2/3 cylindrical to slightly infundibular, 3.75 cm tall, 1 cm wide; upper part abruptly flaring to 4.7(-5) cm wide at the lip; wings or ribs not apparent; mouth orbicular, horizontal, not forming a column for the lid; peristome barely differentiated from rim of pitcher mouth, 0.2 mm wide, lacking teeth or ribs; lid held arched over mouth, linear-oblong, 4.5-5 by 0.2-0.4 cm, lower surface lacking appendages, nectar glands crater-like, sparsely scattered at the margins, elliptic, 0.2 by 0.1 mm; spur linear, 3-4 mm long, reflexed, unbranched. Male inflorescence 17 cm long; peduncle 5 cm long, c. 1.5 mm diam. at base; partial peduncles c. 50, 1-flowered; pedicels 8 mm long at base (4 mm long at apex); bract inserted near the base, small and filiform; tepals oblong-lanceolate, acute, 3 by 1 mm; staminal column c. 4 mm long. Fruits and seeds unknown. Indumentum inconspicuous, puberulent, hairs erect, simple, 1-2 mm long, stems soon glabrescent, but hairs persisting in leaf axils and on pitcher lid, leaves and pitchers glabrous. Colour of pitchers yellowish green, drying blackish brown.A


Nepenthes inermis is most likely to be confused with N. dubia or N. bongso which occur in the same general area of Sumatra and both of which can have similar proportions, indeed, all three species have been united by Tamin & M. Hotta under the name N. bongso. Nepenthes inermis is easily recognised by the absence of a ridged or dilated peristome and by the linear-oblong lid that overarches the mouth.
This species remains poorly known, and as yet the lower pitchers have never been collected. The remarkable upper pitchers lack a peristome, and have a very narrow lid. The tendril may or may not be coiled, an unusual habit — in the majority of species they are always coiled in upper pitchers. The pitcher fluid is said to be extremely viscous, forming long stringy droplets when the pitcher is upset. An unrelated species, N. eymae shares the same combination of infundibulate pitcher, narrow lid and viscous pitcher fluid. It has been suggested, and demonstrated in greenhouse-grown plants, that the infundibuliform pitcher and the highly viscous pitcher fluid allows rainwater to be shed from the pitcher without diluting or washing away the partly-digested contents. The weight of rainwater causes the pitcher to overbalance, shedding the water from the broad mouth, whilst the narrow shape of the lower part of the pitcher, and the viscosity of the column of fluid that it contains, prevents mixing with the supernatant rainwater (Wistuba (1994) 21 September 1994 09:14:56 GMT+1. ‘CP’ Bulletin board: listproc@, archived as CP. 94ALL part [41/55]). A survey of 22 pitchers (under the name N. bongso) suggests that this species traps a very high proportion of dipterans (flies) compared to other Sumatran species surveyed (Kato et al. Trop. Ecol. 6 (1993) 11-25).A

Distribution (General)



Epiphytic in moss forest; 2300-2590 m (Hopkins et al. Carnivorous Plant Newsl. 19 (1990) 19-28).A


A. Cheek, M. R. & Jebb, M. H. P. 2001: Flora Malesiana - Nepenthaceae, Series I, Volume 15. – Leiden: Nationaal Herbarium Nederland, Universiteit Leiden branch


CountryDateCollector + collecting numberHerbariaTypeScanDerivatives
1920-04-26Bünnemeijer 9695BO
Citation: Sumatra, G. Kerinci, alt. 1800 m, 26 Apr 1920, Bünnemeijer 9695

Specimen summary: BO
Lectotype of Nepenthes inermis Danser