Sumatra and Peninsular Malaysia based on 70 morphological characteristics of each taxon. The following is a portion of the resultant cladogram, showing part of "Clade 5", which has 69% bootstrap support. The sister pair of N. rafflesiana and N. sumatrana has 58% support. N. beccariana was not included in this study. Seedlings of N. adnata and N. longifolia are virtually indistinguishable, although mature plants have few morphological features in common. Clarke writes that N. longifolia is likely to be one of the closest relatives of N. adnata. Natural hybrids Despite occurring sympatrically with a number of other Nepenthes species, N. longifolia appears to hybridise very rarely; only one natural cross with N. eustachya is known with confidence, although it may also hybridise with N. sumatrana. Nepenthes eustachya × N. longifolia has been recorded from a number of locations near Payakumbuh and Sibolga, where its parent species are sympatric. It is relatively rare because N. eustachya and N. longifolia occur in markedly different habitats; the former usually grows in exposed, sunny sites, while the latter is more common in dense, shady forest. This hybrid differs from N. eustachya in having fringed lamina margins bearing short reddish-brown hairs. The peristome often has a distinctive raised section at the front, a characteristic inherited from N. longifolia. It can be distinguished from N. longifolia on the basis of its shorter tendrils and the presence of longitudinal furrows on the surface of the lamina, similar to those of N. eustachya. Notes a.Meijer explored the forest of the Tjampo region between August 20 and August 28. He collected N. longifolia on August 24 together with the type material of N. adnata and N. tenuis. b.The original Latin description of N. longifolia reads: Folia mediocria, lamina oblongavel lanceolata, nervis longitudionalibus utrinque 3-4, basi in alas 2 decurrente ; Ascidia rosularum mediocria, parte inferiore ventricosa os versus cylindrica, ails 2 fimbriatis; ascidia facie ventrali sub peristomio elevata quomodo peristomio inter alis distinctissime undulato, operculum versus acuminato et elevato, ad 6 mm lato, costis 0,2 mm distantibus , dentibus 0. Operculo orbiculari, facie inferiore plano. Ascidia superioria magna, e parte inferiore anguste infundibuliformi tubulosa, costis 2 prominentibus, ascidia facie ventrali sub peristomio elevata quomodo peristomio inter alis distinctissime undulato, operculum versus acuminato et elevato, ad 6 mm lato, costis 0,2 mm distantibus, dentibus 0. Operculo orbiculari, facie inferiore piano. Inflorescentia racemus, pedicellis 1-1,2 cm longis, omnibus 2-floris. Indumentum parcum