ROOT AND CROWN. 61 



and lap over each other, so that the rain which 

 strikes on any one of the upper leaves of the tree 

 runs down to the apex of the leaf, where it collects 

 in the form of a drop, and falls on the shelving 

 surface of a leaf below. There it unites with 

 freshly fallen water, and so descends from step to 

 step, drawing ever nearer to the edge of the tree, 

 till it finally shows itself in a number of little 

 cascades on every side. 



From the lower, outer leaves of the whole crown 

 the water falls on the earth, and the dry ground 

 under the tree is enclosed after every rain by a 

 zone of thoroughly wet soil. If we dig in these 

 wet places, we find that the young roots with their 

 absorbing fibrils have penetrated just as far as this 

 wet zone. In young trees, where the rootlets are 

 near the tree trunk, the crown is less spreading 

 and the wet zone is of correspondingly small cir- 

 cumference. But as the reach of the drip widens, 

 the roots, seeking moisture, also extend, and roots 

 and leaves actually keep step in their outward 

 growth. It seems to me probable that the gar- 

 dener's custom of pruning the branches and roots 

 of the trees which he transplants is for the purpose 

 of bringing them into accordance with this law. 

 Practically, the gardener or farmer always observes 



