424 Macfarlane —Observations on Pitchered 
a common origin, though their geographical distribution is now 
so diverse. 
Lastly, N. Lowii is very difficult to connect with other 
species, and seems early to have branched off from a primitive 
type. 
On page 425 I have arranged a chart which gives the struc- 
tural relations of the species, and though it would be rash to 
assert that it is genealogically correct in every connexion, 
I think it may fairly and approximately be taken to represent 
the leading lines of development followed in the evolution of 
the species. As explained later on, a complicating factor is 
introduced in the ease with which Nepenthes hybridize, and 
there is some difficulty in ascertaining what may be regarded 
as species capable of perpetuating themselves. 
The more general consideration of the histology of Nepenthes 
may now be entered upon. 
(a) Vascular supply, A special feature of the genus Ne- 
penthes is the intimate relation which the vascular system 
bears to the glands. In Sarracenia and Davlingtonia the 
glands are never connected with the vascular system ; in the 
more complex lid-glands of Heliamphora I have repeatedly 
observed that vascular bundles pass behind or appear to 
end in them, but my material has been insufficient to 
assure me. 
In Nepenthes every gland is directly seated on a vascular 
bundle, or a vascular diverticulum ends beneath it. This fact 
is beautifully demonstrated if pitchers are macerated in the 
manner recommended in Part I of this paper (Annals of 
Botany, Vol. iii, p. 254), and are gradually dissected from 
without. A xylem and phloem portion are readily distin- 
guishable by their respective elements in any bundle near the 
base of an alluring, attractive, or digestive gland, but the 
direct junction consists of slightly elongated cells with dense 
protoplasmic contents. The vascular supply to the marginal 
glands is, as we might expect, most complex. Each ridge of 
the corrugated collar is traversed internally by a strong 
bundle given off from a common encircling one, and this, 
