AN APPLE ORCHARD SURVEY OF WAYNE COUNTY, NEW YORK. 279 



The living and growing part of a tree is the cambium layer. This 

 is a tissue lying upon the outside of the wood and beneath the bark. 

 From its outside it produces bark, and from its inside it produces wood. 

 It is this layer of young, tender cells that makes the barkr" slip " so readily 

 in early summer. The inner part of the tree is not active ; its value to the 

 tree is in supporting the living part. If this center part decays, the tree 

 usually continues to grow till it breaks down (see Fig. 52). 



This dead inner wood is protected by the bark and living portion 

 so that fungi and bacteria cannot reach it. When a large limb is 

 removed the seal is broken and the dead wood is exposed. Having 

 no life, it cannot resist infection by germs any more than a dead log 

 can do so. The safety of the tree depends on having the wound 

 healed over before it becomes infected. The wound heals by the 

 growth of the cambium layer. If the wound is small it will usually 

 be sealed up before the fungi get established ; but if the dead stub is 

 exposed for a long time the wood-rot fungi are almost certain to attack it 

 and cause the trunk to decay. If the wound does then heal over, the 

 mycelium of the fungi is established and may continue to grow within the 

 tree.* The decay may reach into the living tissue, but its most serious 

 effects are in so weakening the trunk as to cause it to break down. In 

 order to avoid the rotten trunks -that are so common in the majority of 

 the orchards, three things should be observed : 



1. Large limbs should not be removed unless it is absolutely necessary. 



2. When such limbs must be removed, the pruning should be so done 

 as to favor rapid healing of the wounds. 



3. Large wounds should be protected by paint till the tree can seal 

 them. 



The removal of large limbs. T\\t ideal way would be to have the 

 tree so pruned from the time it is planted that there would never be 

 occasion for the removal of large limbs. But very many orchards 

 were neglected so long that it may be necessary to cut out such limbs. 

 Eighteen per cent of the orchards are still practically unpruned. In 

 a neglected orchard some limbs may be damaged by neglect or lack 

 of food. Others die as a result of the shade caused by dense tops, or 

 the trees being too close together. Even in a well cared for orchard 

 an occasional limb will be broken by the wind, or by too heavy a load 

 of fruit, or will die from other causes. But much of the removal of 



*Cornell Bulletin 193, Shade Trees and Timber-Destroying Fungi. 



