AMENTACB^ 



361 



twig is somewhat stouter, say '09 of an inch. Follow- 

 ing this up, we shall find that, ccBteris paribus, the 

 size of the leaf has relation to the thickness of the 

 stem. 



Of course, however, this is only approximate. Other 

 things have to be taken into consideration. Strength, 

 for instance, is an important element. If, for example, 

 we compare the Beech and Hornbeam with the Lime 

 (p. 31), the general plane of the leaves is again that of 



Fig. 249.— Beech. 



Fig. 250. — Spanish Chestnut. 



the branch (Fig. 249) ; but the leaves themselves are 

 ovate in form, and smaller, being only from 2 to 3 inches 

 in length. On the other hand, the distance between 

 the nodes is also smaller, being, say, 1^ inch against 

 something less than 2 inches. The diminution in length 

 of the internode is not, indeed, exactly in proportion to 

 that of the leaf, but, on the other hand, the leaf does 

 not make so wide an angle with the stem. To this 

 position is probably due the difference of form. The 

 outline of the basal half of the leaf fits neatly to the 

 branch, that of the upper half follows the edge of the 

 leaf beyond, and the form of the inner edge being thus 

 determined decides the outer one also. But it may be 



