SEEDS SOILS TRANSPLANTING! 53 



the course of growth or fruiting or they are stored 

 up for next season's work. In the northern tem- 

 perate regions food which is manufactured in the 

 leaves is carried in quantity to the roots during the 

 months of July, August, and September. In the 

 springtime the stored food is reconverted into more 

 soluble forms and is then transported to the upper 

 part of the plant to supply the needs of the season's 

 work. Some of the food is used by the roots for 

 their own purposes of increase. The movements of 

 food correspond to sap movements and relate largely 

 to the laws of diffusion. Thus when there is an ex- 

 cess of a mineral salt in the upper part of a plant it 

 would naturally move downward in order to meet 

 the water from the root containing a lesser solution 

 of the salt. We need not at this point go into the 

 elaborate and more complex physiology relating to 

 sap movements. In a young tree nearly all of the 

 food is needed for maintaining life processes and 

 constructing new tissue. When sufficient volume of 

 new tissue has been laid down the plant then acquires 

 a surplus of food and reproduction begins. This 

 explains the earlier fruiting of trees which have had 

 plenty of nourishment in the course of cultivation. 

 It explains in part the earlier bearing of grafted 

 trees, the stocks having an advantage in age over 

 the top. Another reason for early bearing of grafted 

 trees is that bearing branches or branches nearly 

 ready to bear are commonly chosen as grafts. The 

 cell structure of such grafts has become already 

 formed for fruiting purposes. 



