state; i'OmoIvOGical soctkty. 125 



to place the food materials where they will do the most good 

 they should be distributed all over the ground shaded by the 

 foliage and particularly upon the outer portions of this area. 



Ater the solutions of food materials are absorbed they pass 

 aloug to the cells adjoining the root hairs and then upward 

 through the roots and trunk and branches in the wood inside the 

 cambium zone, and then outward into smaller and smaller 

 branches till they reach the leaves. These are the laboratories of 

 the tree where the actual manufacture of the food for the nour- 

 ishment and building up of the tissues takes place. In these leaf 

 laboratories the more simple chemical compounds brought up 

 in solution from the soil are combined with some of the water 

 itself and with the carbon dioxide of the air into the much more 

 complex food substances. Sunlight is the ultimate source of 

 energy for this process and it cannot take place without it. 



Thus we readily see the necessity for pruning. While prun- 

 ing is of great advantage in removing dead, diseased and surplus 

 wood and in providing opportunity for the better coloring of 

 the fruit, it is absolutely essential to ensure the most efficient 

 and maximum production of food substances. In a thick topped 

 apple tree only the outer leaves receive the full rays of the active 

 summer sunlight. Those within are so shaded that they fall far 

 short of working to their full capacity and almost may be 

 classed as non-producers in this great leaf community of plant- 

 food manufacturers. Moreover such leaves must of necessity 

 be weaklings for their own tissues are dependent for nourish- 

 ment upon the food which they manufacttire. The apple scab 

 fungus which is one of the greatest enemies of the apple tree 

 in Maine finds among them the ideal conditions under which to 

 gain a foothold. This fungus loves shade and moisture, while 

 free access of sunlight and the free circulation of air through 

 the tree-tops are of great assistance in keeping it in check. 

 It more readily attacks the leaves that are in a weakened condi- 

 tion and a leaf so attacked rapidly loses its food manufacturing 

 ability. Hence the attacks of apple scab indirectly deprive the 

 tree of its tissue building materials. 



A well pruned, well shaped, open-topped apple tree allows 

 the admission of sunlight to all of the interior portions. The 

 limbs are so arranged that the maximum number of leaves are 

 exposed to the source of energy and they are thus worked to 



