226 APPLICATION OF PRINCIPLES. 



Whenever the stock and graft or bud are not per- 

 fectly well suited to each other, an enlargement is 

 well known always to take place at the point of their 

 junction, and generally to some extent either above 

 or below it. This is particularly observable in Peach 

 trees which have been budded, at any considerable 

 height from the ground, upon Plum stocks ; and it 

 appears to arise from the obstruction which the de- 

 scending sap of the Peach tree meets with in the bark 

 of the Plum stock ; for the effects produced, both 

 upon the growth and produce of the tree, are simi- 

 lar to those which occur when the descent of the 

 sap is impeded by a ligature, or by the destruc- 

 tion of a circle of bark. In course of time this 

 difference between the scion and stock puts an 

 end to the possibility of the ascending and de- 

 scending fluids passing into each other, and the 

 death of the scion is the result. In all the cases I 

 have seen, this has arisen from the power of hori- 

 zontal growth in the stock and scion being different; 

 and I doubt whether it ever proceeds from any other 

 cause. For example : the Hawthorn and the Pear 

 are so nearly allied that the latter may be easily work- 

 ed upon the former; the Hawthorn is, however, a 

 slow-growing bush or small tree ; the Pear is a large 

 forest tree of rapid growth ; and the Pear will grow 

 an inch in diameter while the Hawthorn is growing 

 half an inch. 



This last circumstance, if the difference in the rate 

 of growth or in other respects is not excessive, may 

 be taken advantage of for particular purposes. When 



