PRUNING. 103 



woody fibre at the top is as great as, and it may be 

 greater than, at the bottom ; and hence it bends under 

 its own weight. 



2d. The tendency of the sap to the growing points 

 at the top of the tree. Growth is always the most ac- 

 tive and vigorous at the newly formed parts, when trees 

 are in a natural condition. The young buds are the most 

 excitable, and the more direct their communication with 

 the roots, the more rapid will be their growth. Hence 

 it is that a yearling tree, furnished with fifteen to twenty 

 buds or more, from its base to its top, frequently produces 

 a shoot from its terminal bud only, and seldom more than 

 three or four shoots from the whole number of buds, and 

 these at the top. This natural tendency, and the exclu- 

 sion of light from the stems of nursery trees by their 

 closeness to one another, are the chief causes of weak 

 and crooked trees, to counteract which we resort to 

 pruning. 



In " heading down " a young tree, we cut away one- 

 third or one-half of the length of the stem, and this removes 

 the actively growing parts. The sap must then find new 

 channels. Its whole force is directed to the buds that were 

 before dormant ; they are excited into growth, and produce 

 new wood and leaves ; these send down new layers of 

 woody fibre on the old stem, and it increases rapidly in 

 diameter, so that by the time it has attained its former 

 height, the base is two or three times as thick as the top, 

 and possesses sufficient strength to maintain an erect 

 position. 



Maintaining an equal Growth among the branches of a 

 tree is conducted on the same principle. Branches that 

 are more favorably placed than others, appropriating more 

 than their due proportion of the sap, and growing too vig- 

 orously, are checked by removing more or less of their 

 growing points ; this lessens the flow of sap to that 

 point, and it naturally takes its course to the growing 



