THE SEEDLING AND YOUNG PLANT. 47 



stem from the insertion of a leaf is spoken of collect- 

 ively 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 two fifths, 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 leaf 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 downward, 

 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 center 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 is 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 bun- 



