248 Bower . — On the Pitcher of Nepenthes : 
Now, because certain modes of localisation of growth in the 
developing leaves are common, and since accordingly in large 
and complicated leaves the parts above distinguished usually 
have a certain conformation, it does not follow that this should 
always be the case. But the attempt made by most writers 1 
to homologate the parts of such a peculiarly developed leaf as 
that of Nepenthes with the parts of leaves of the usual type, 
implies the assumption that it is possible to make the dis- 
tinction in every case, and that the parts thus recognised are 
in some recondite way different from one another. In the 
absence of evidence that Nepenthes is descended from ancestors 
with a normal petiole, which in this plant became widened 
into its well-known expanded base, it will be well, I think, to 
give up the attempt to homologate the parts of this phyllo- 
podium with those of the ordinary type. It was the unnatural 
extension of a generalisation, based on wide but not universal 
experience, to all cases, that ruined the spiral theory of Braun 
and Schimper ; and in the case of the leaf the extension of 
the notion of transverse limitation must have like results. 
While we note that a distinction of petiole and lamina, as 
parts having usually a definite relation of form and position, 
is applicable to a large proportion of leaves, let us beware of 
assuming that the parts of all leaves, however peculiar their 
form, are referable to such a type. 
To meet the difficulty of want of uniformity in different 
leaves, and especially in cases such as that now under discus- 
sion, it is, I think, important to fix the attention upon the 
phyllopodium throughout its length. It is, as a rule, a structure 
which is traversed by two longitudinal wings ; such wings, or 
longitudinally directed flanges, are to be found in a very large 
proportion of leaves, from the lowest Ferns to the Dicoty- 
ledons, and, though not universal, the prevalence of this winged 
character is a much more constant and important phenomenon 
than those on which the distinction of sheath, petiole, and 
3 Drude and Goebel both attempt to define limits of petiole and lamina in 
Nepenthes. 
