THE SEEDLING AND YOUNG PLANT 47 
tively as the ‘ leaf-trace.’ Hence we see the leaf-trace 
of the oak consists of five bundles —one median, two 
lateral median, and two lateral—and since the phyllo- 
taxis of the oak is 2, there will be twenty-five bundles 
in various stages of separation or conjunction coming 
down in the five internodes between any one leaf and 
the lea: vertically above it, as well as the parts of 
bundles from other leaves which are still continuing 
their course for a short time. 
Now, since the main lengths of the course (in the 
stem) of these bundles is nearly vertically downwards, 
with slight swerves to one side or another as the strands 
join, it is obvious that on the transverse section of the 
stem the bundles will appear arranged in a series round 
the centre—in fact, they will form on the whole a more 
or less regular ring of bundles dividing off the pith from 
the cortical portions of the stem. Even in the very 
young condition (fig. 9) we see bundles or groups of 
strands thus surrounding the pith, only the ‘ring’ 
which they make is a sinuous one, so that the pith 
is five-rayed—a characteristic point in the oak. At 
a slightly later stage, as we shall see, this ring of 
bundles becomes more nearly circular from the gradual 
filling up of irregularities. 
Before proceeding further it 1s necessary to make 
clear one or two other points. Since all the vascular 
bundles in the oak-stem are bundles which are common 
to the stem and leaf, they are termed ‘common bundles.’ 
We have seen that a given strand or bundle may run 
