PRINCIPLES OF GRAFTING. 



219 



two kinds, but also the difference in the general character of 

 their growth. It is essential, that the 

 stock and graft should be naturally 

 in sap at the same time ; and this is 

 more likely to be the case in nearly 

 allied species than in others. How- 

 ever, in very succulent plants, such as 

 the Cacti, of which the fleshy stems 

 are always full of fluid, grafts of very 

 different species succeed well toge- 

 ther ; and this exception helps to prove 

 the rule. It is necessary, also, that 

 the rate of growth of the two should 

 be nearly the same ; for, if the graft 

 be of more rapid growth than the 

 stock, and more be sent down to the 

 latter than it can convert into tissue, * ^ ^ 



a swelling will be formed above the pERI , ENDIcm !l 8ECTION 0(r A 



line pf Union, like that which takes GRAFT INSERTED ON A DWARF 



place when a cord is bound round a 



stem (. 144) ; and this will increase, so as in time to cause the 

 death of both parts, by altogether obstructing the passage of fluid. 

 351. Not only does the process of grafting enable the gar- 

 dener to multiply with greater rapidity, and to preserve with 

 more certainty, any valuable kinds of flower or fruit ; but, by 

 the judicious selection of a stock, a favourable influence may be 

 produced upon them. Thus, the more delicate kinds of Vines 

 produce larger and finer grapes, when worked upon coarser and 

 more robust kinds ; and the Double Yellow Rose, which seldom 

 opens its flowers, and will not grow at all in many situations, 

 blossoms abundantly, and grows freely, when grafted on the 

 common China Rose. Some statements, however, which im- 

 pute to the stock a much greater influence, are without any 

 foundation in truth. Thus, it has been asserted that Roses 

 become black, when grafted on Black Currants ; and Oranges 

 crimson, if grown upon the Pomegranate : but this is altogether 

 erroneous, as these species will not unite at all. 



