184 LUTHER BURBANK 



tomato roots. But the root system of any tree 

 requires nourishment if it is to develop, and this 

 nourishment, as we have seen, must be supplied 

 by the leaves of the tree above it, even though 

 the roots themselves first collect part of the 

 materials. 



It follows that the root system of any tree, 

 while it is absolutely essential to the leaf system 

 above it, is also very largely dependent on that 

 system. 



In other words, there is the closest recip- 

 rocal relation between root system and leaf 

 system. 



This relationship, which many orchardists 

 overlook, has been long recognized and re- 

 peatedly referred to. But the case of the to- 

 mato on the potato root emphasizes the lesson 

 in such terms that no one can ignore it. With 

 this illustration before us, we can scarcely doubt 

 that the root system of any stock on which a for- 

 eign top is grafted (as is the custom in most 

 orchards) is modified in some measure by the 

 cions it bears. The foreign leaves cannot supply 

 precisely the same quality of nourishment to the 

 root that learves of its own kind would have 

 supplied. 



In the main, no doubt, the protoplasm of the 

 root assimilates the nourishment that comes to 



