NATURE OF PLANTS 



99 



istic tissues already noted in the leaves and su-nis; while a cor- 

 responding growth in the cortex and adjacent regions results in 

 the formation of vascular bundles that connect the vascular 

 bundles of the stem with those of the leaves and branches. When 

 a leaf falls off, the ends of these vascular bundles can be easily 

 seen in the leaf scar (Fig. 28, A) but owing to their minuteness 



Fig. 63. Diagram of the tip of a stem as seen in longitudinal section: 

 a, formative region corresponding to the part shown in Fig. 61; /, b, leaves 

 and branches in various stages of development; v, vascular bundles; c, cortex; 

 p, pith. 



it is not an easy matter to trace them through the stem to the 

 point where they join on to the bundles of the stem. In the 

 branch, however, owing to its size and woody character, the 

 union with the stem is very manifest. Fig. 64 shows several 

 very small branches that continued to keep pace for one or more 



