The Leaf 



111 



of maple looked at from above shows the same thing. 

 The lower leaves, instead of being completely over- 

 shadowed by the upper ones, are furnished with longer 

 stalks, which enable them also to catch the sunlight 

 from above. 



In order to grow well some kinds of trees want more 

 light than others do, and if other trees grow too closely 

 round the light-loving ones those branches that are 



Fig. 55. Elm twig, showing leaf mosaic. 



overshadowed will not grow as freely as those that 

 are exposed to the sun and air. It has been found that 

 the shade-bearing trees are those which, like the beech, 

 themselves cast the deepest shade, while the trees 

 with light crowns will not grow under more thickly 

 leaved ones. This is probably because in a perfectly 

 natural state trees grow in a clump with others of their 



