CHAP. IV. FUNCTION OF NUTRITION. 233 



within a short distance of the ground ; then hollowing 

 out the stump and planting within it several young 

 trees of different species and families. In a few years 

 the whole grow up together so as completely to fill the 

 cavity, and on a superficial observation appear to have 

 become blended or grafted into a single stem. The 

 deception is still more perfect if a few buds have been 

 left upon the stump to keep this alive also. 



(228.) Kinds of Grafts. M. Thouin has de- 

 scribed about a hundred different ways in which the 

 process of grafting may be varied. These may however 

 be referred to the three following general classes. 



1 . By Approach. Two plants are placed near 

 each other, and their boughs grafted together whilst 

 they are still on the stems. When they have become 

 completely united, one is then severed from its own 

 stock and left to grow on that of the other. 



2. By Slips. A shoot is taken from one tree and 

 placed on the extremity of a branch of another properly 

 prepared to receive it. The branch is cleft and the 

 graft inserted into the notch in various ways, which 

 more peculiarly form the study of the gardener. This 

 graft is made in the spring when the sap is rising. 



3. Budding. A piece of bark is removed from a 

 tree at a place where there is a bud ; and a piece of the 

 same dimensions is taken from another tree also con- 

 taining a bud and is then placed on the exposed alburnum 

 of the former tree. The branch is tied tightly above 

 the graft in order to force the rising sap into it. This 

 graft is practised both in spring and autumn. 



(229.) Effects of Grafting. It does not appear that 

 the graft produces any decided effect upon the stock, as 

 we have already remarked (art. 224.) ; but in certain 

 instances the reverse seems unquestionably to be the case. 

 The influence is rather to be attributed to some dif- 

 ference in the mode of growth in the two subjects, 

 than to any dissimilarity between the two saps of the 

 stock and graft. Thus the lilac grafted on the ash be- 

 comes a tree, and the Mespilus japonica on the haw- 



