Danser's Monograph on Nepenthes: Nepenthes dubia

11. Nepenthes dubia DANS., spec. nova.

Icon: nostra 4.

Folia mediocria sessilia, lamina lanceolato-spathulata, nervis longitudinalibus utrinque c. 3, basi attenuata 1/3-2/3 caulis amplectente, vagina 0 ; ascidia rosularum et inferiora ignota ; ascidia superiora parva, parte inferiore tubulosa v. leviter ventricosa, supra medium infundibuliformia, costis 2 prominentibus ; peristomio fere horizontali, operculum versus acuto, applanato, 2-4 mm lato, costis 1/2-1/4 mm distantibus, dentibus 0 ; operculo anguste cuneato, facie inferiore plana ; inflorescentia ignota ; indumentum parcum, iuventute tomentum fuscum, denique deciduum.

Stems climbing, slender, the part with adult leaves cylindrical or slightly angular, 3 to 4 mm thick, the internodes about 3 to 10 cm long. Rosettes and basal part of the stem unknown. Leaves of the climbing stems scattered, thin-coriaceous, sessile, lanceolate-spathulate, mostly 6 to 10 cm long, 1.2 to 1.8 cm broad, acute, attenuate at the base, clasping the stem for 1/3 or 1/2 without sheath ; nervation indistinct, the pennate nerves oblique, irregularly reticulate, the longitudinal ones about 3 on both sides, originating from the basal 1/3 part of the midrib, approaching the margin towards the apex ; tendril once to twice as long as the leaf, the pitcher-bearing ones with or without curl. Pitchers of the climbing stems gradually originating from the hanging end of the tendril, incurved with a 5 to 10 mm wide curve, tubulose or slightly ventricose in the lower part, 0.8 to 1 cm wide, infundibulate above the middle, 2 to 3 cm wide at the top, with 2 indistinct ribs ; mouth ovate, acute towards the lid,

. Fig. 4. Nepenthes dubia 2/3 x


horizontal or almost so ; peristome flattened, involute at the outer margin, up to 4 mm broad in front, up to 2 mm broad near the lid, the ribs 1/2 to 1/4 mm apart, the interior margin entire ; inner surface of the pitcher with numerous small slightly or not deepened glands, about 600-900 on 1 cm2 ; lid narrowly cuneate, up to 4 cm long, up to 0.7 cm broad, rounded at the apex, gradually attenuate towards the base, with numerous small round or elliptical glands on the underside, spur 3 to 5 mm long, filiform, inserted close to the lid. Inflorescence &c. unknown. Indumentum very sparse, a loose rusty tomentum on the stems above the axis a dense, brown, appressed pubescence on the young pitchers, disappearing later. Colour of herbarium specimens fallow-dun, here and there blackish. (Description after the under mentioned specimens.)

SUMATRA. Res. Westcoast: G. Talakmau, 1900 m, 29 V 1917, BÜNNEMEIJER 938, H. B. (0). H. L. B. (0).

N. dubia strongly resembles the striking N. inermis, but the difference is too large to unite these two species. N. inermis, like N. Lowii has only a rudiment of a peristome. N. dubia has a broad and flat one. There are, however, also differences in the other parts: the pitchers are less widely infundibuliform and the lid is not so narrow as in N. inermis. Perhaps N. dubia is a hybrid of N. inermis and another species with normal peristome and in that case N. Bongso could be the other parent species, the more so as the vegetative parts of N. inermis, N. dubia and N. Bongso are very similar, and between the other species of the gymnamphora-group intermediate forms often occur.

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