PROPAGATION. 75 



foimed upon the cut surface, and the intercommunication 

 takes place through them. Hence we have anatomical 

 limits to grafting ; there are physiological bounds beyond 

 ■which we cannot pass, in our combinations of scion and 

 stock. Our success is in the direct ratio of the affinity 

 lliat exists between them ; thus apple grows best on apple, 

 and even among these we find the closest union and the 

 best results, where there is a similiarity between the style 

 of growth, and probably in the character of the cells. 



"We say, as a general rule, that stone fruits must be 

 grafted upon stone fruits, those bearing seeds, upon seed 

 fruit ; but there are limits even here which confine us up- 

 on one hand, and give us more latitude upon the other. 

 Thus the cherry may be workeil upon the wild cherry 

 {IVunua Virginiana,) but it forms a very poor union ; the 

 pear will grow upon the thorn, whi^h has a very different 

 seed, but the union is very im.perfect and the tree is short- 

 lived ; the apple would appear to be much nearer of kin, 

 since it belongs to the same genus, but though the pear 

 will grow vigorously upon this stock, it is no more per- 

 manent than upon the thorn : either of them will answer 

 when grafted low, or in the root, to start the cutting, as 

 the scion may then be considered, and to sustain it until 

 it shall have supplied itself with roots. In top-grafting 

 the pear upon a tree of either species, it is found essential 

 to success, and it conduces to the greater durability of the 

 tree, for some branches of the original stock tp be left in- 

 tact to secure the circulation of the trunk, as the union of 

 the dissimilar cells is so imperfect that it does not furnish 

 sufficient vent for the sap. In the case of the cherry we 

 find that the varietiyes appear to have a greater affinity 



