certain Orders of the Ranales. 66 5 
two structures as essentially two, for physiological purposes, interrupted 
parts of one and the same primitive and ancestral cylinder. 
The leaf-base more than half embraces the stem ; this character, 
together with the large size of the petiole-bundles as compared with those of 
the stem , clearly give the impression of the leaf being the more important 
of the two organs, viz. the one which is likely to have given character and 
origin to the other, rather than the reverse. 
In the peduncle 3 concentric bundles constitute the only foliar-traces ; 
some of them are large, others are very small ; they leave the cylinder as 
arc-shaped strands, which soon close up and enclose a pith (Fig. 23). They 
eventually enter the sepals of the flower, each breaking up into a number 
of collateral bundles. Their interpretation is the same as for the vege- 
tative stem. 
Bibliography. 
Goffart : loc. cit. Meyer : loc. cit. Petit : loc. cit. Sterck : loc. cit. 
MAGNOLIACEAE. 
In spite of the fact that the plants of this order are trees and shrubs, 
there is considerable evidence, both in the external morphology and the 
internal vascular anatomy, that the entire stem is built up of a succession 
of phytons, each segment having primarily terminated in a leaf. The large 
size of the leaves, the way their petiole-bases, by means of their stipules, 
completely embrace the stem, point to the fact of the leaf having been the 
dominant organ of the plant, to which the stem was subservient. This is 
well brought out, as will be seen below, by the study of the vascular 
structure of stem and leaf. 
In the preservation, in the young stem, of the individuality of the 
bundles of the cylinder, and in their somewhat irregular size and arrange- 
ment, we see traces of the primitive scattered system in the central cylinder. 
Hence I conclude that the arborescent habit of the plant is derived and not 
primitive. 
Magnolia tripe tala, L. 
I will take this species as typical of the genus. 
Leaf : In the midrib of the lamina is a complete cylinder of bundles. 
About half-way down the petiole five or six of these bundles pass into the 
pith and remain there, all situated on the dorsal side, until such time as 
the petiolar strands enter the stem ; this structure is probably a remini- 
scence of the primitive scattered system of the herbaceous ancestor. 
Stem : At the junction with the stem these medullary bundles again fuse 
