140 THE BEAUTIES OF NATURE CHAP, 
the general plane of the branch, which bends 
slightly at each internode.. The basal half of 
the leaf fits the swell of 
the twig, while the upper. 
half follows the edge of 
the leaf above; and the 
form of the inner edge 
being thus determined, 
decides that of the outer 
one also. 
The weight, and con- 
sequently the size of the 
leaf, is limited by the 
strength of the twig; and, 
again, in a climate such as 
ours it is important to plants to have their 
leaves so arranged as to secure the maximum 
of light. Hence in leaves which lie parallel to 
the plane of the boughs, as in the Beech, the 
width depends partly on the distance between 
the buds; if the leaves were broader, they 
would overlap, if they were narrower, space 
would be wasted. Consequently the width 
being determined by the distance between the 
buds, and the size depending on the weight 
Fig. 15.— Beech. 
