Cephalotus to those of Nepenthes, leads to a comparison in the first place of these two genera. But although both are apetalous, and in the parts of the flower deviate from the quinary or prevailing number in Dicotyledones, yet they 317] differ in so many other important characters that they cannot be considered as nearly related.
The place of Nepenthes in the natural series I have long since[1], in my account of Rafflesia, suggested to be near Aristolochiæ or Asarinæ, without, however, intending to include it in that family.
This approximation was adopted by M. Ad. Brongniart, who, however, went further, having absolutely referred Nepenthes to Cytineæ.
The union of plants so utterly unlike in appearance and œconomy, and so different, it may be added, in many of their most important characters, seems to have been generally regarded as somewhat paradoxical; and accordingly Professor Link, in 1829, has established Nepenthes as a section or tribe of Aristolochiæ, and Dr. Bartling and Mr. Lindley, in 1830, have considered it as forming a distinct natural family.
To the numerous and obvious distinctions between Cytineæ and Nepenthes may be added the no less important differences in their internal structure. For while Cytineæ, like most, perhaps all, other plants parasitical on roots, are destitute of spiral vessels, Nepenthes exhibits these vessels in the greatest degree of development and abundance, and also produces them in parts in which they are hardly to be met with in any other dicotyledonous plant.
Thus, in addition to the dense circle or stratum of spiral vessels existing in the stem between the outer parenchyma and the wood, they are found also singly or scattered in the pith, in the loose parenchyma situated between the wood and the bark, if it may be so called, even in the fibres of the root, and everywhere in the substance of the leaves, the pitchers, calyx and capsules. And between these solitary or scattered spiral vessels, which are often of considerable
- ↑ Transact. Linn. Soc. vol. xiii, p. 219 [vol. i, p. 386].
