June, 1916] Starch in Apple Trees 359 



reaches other portions, causing decay of the plant tissues, and 

 very soon the body of the tree becomes a shell. The sap wood 

 remains actively engaged in the functions necessary to the life 

 of the tree, and fungi do not so easily get hold. This gives us 

 the shell condition of the apple tree, which is so common in old 

 orchards where wounds to the tree are neglected, and incident- 

 ally, artificial roadways made to the heartwood of the tree for 

 the access of fungi. 



In summary, it ma}^ be stated that, during the dormant 

 period, starch reserve is stored in the living cells of the pith, 

 wood parenchyma, and medullary rays of the apple. With 

 approach of spring, starch is found in the tissues of the bark, 

 appearing first in the phelloderm and collenchyma. 



As the leaves begin to appear, starch begins to disappear 

 from the various tissues in order as follows: bark, wood 

 parenchyma, rays, pith. It is used first from the youngest wood 

 of the branches in the top of the tree, later, from the lower 

 portions of the tree, and finally from the roots. 



A portion of the starch reserve may never be used in the 

 growth of the tree, but remains behind to be included in the 

 heartwood where it remains indefinitely and renders the wood 

 susceptible to decay. 



Purdue University. 



