THE SEEDLING AND YOUNG PLANT 47 



lively 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 f, 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 leai 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 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 bundles.' 

 We have seen that a given strand or bundle may run 



