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now existing, in which many middle-aged trees, of 

 diseased and unproductive varieties, are not to be 

 found. These should be immediately regrafted ; but 

 unless this operation be performed with more judg- 

 ment than usually belongs to the common grafter, it 

 will often be fatal to the tree. The grafts will, how- 

 ever, almost always succeed during the first three or 

 four years, together with the stock. It not unfre- 

 quently happens that the scions inserted belong to as 

 old, and as diseased, a variety as that which has been 

 taken off ; and, in this case, the graft and the stock 

 appear to die by mutual consent. When old trees 

 are to be grafted, the scions of a very young and 

 hardy variety, of extremely vigorous growth, should 

 be selected ; and the grafts should be inserted in the 

 large branches at some distance from the trunk ; and 

 never, vvhere it can be avoided, in the principal stem 

 itself. Large scions should be used, for these take a 

 deeper and firmer hold of the stock than small ones. 

 The thick covering of lifeless external bark should, 

 at the same time, or in the succeeding winter, be totally 

 pared off, care being taken that the internal bark be 

 not anywhere cut through. The effects of this opera- 

 ration will be found extremely beneficial to the tree 

 in its future growth, and it will not be difficult to trace 

 these effects in their cause. From very numerous 

 experiments on the ascent and progress of the sap in 

 trees, made by means of coloured infusions, and by 



