OBSTRUCTING THE SAP 161 



five is to withhold tillage or manure. Another 

 motive for heading-in is merely to keep the tree 

 in shape, or to trim into some desired form. This 

 is a matter of a personal ideal, and, although the 

 writer's ideal is counter to this, there is no arbi- 

 trary standard by which the one ideal or the other 

 is to be judged. The writer believes that an open- 

 centered and free -growing fruit-tree is generally 

 preferable to a compact -headed and sheared -in 

 tree, but most excellent commercial results, par- 

 ticularly in stone-fruits, are often secured under 

 the latter method of tree-growing. The orchardist 

 should determine his own purpose when he begins 

 to prune his trees, and then carry out his plan 

 systematically and logically to the end. Aside 

 from these purposes, there remain the necessary 

 heading-in of dwarfs (Chap. V.) and the heading-in 

 for production of fruit -buds (Section 15). 



10. An obstruction just above a bud or limb 

 tends to produce strong longitudinal growth 

 in that part ; an obstruction below it tends 

 to produce a thickening of the part and a 

 quiescent state. 



The obstruction below the bud tends to cut off 

 the supply of water, upon which rapid growth 

 largely depends ; but the deposition of elaborated 

 materials from the leaves builds up tissue. 

 Since rapid wood growth is hindered because of 

 the obstruction to the up ward -moving sap, the 



