28 



ARTIFICIAL PROPAGATION 



70. Plants have preferences as to the stocks on which 

 they will grow ; but we can find out what their choice is 

 only by making the experiment. The pear grows well 

 on the quince, but the quince does not 

 grow so well on the pear. The pear grows 

 on some of the hawthorns, but it is an un- 

 willing subject on the apple. Tomato 

 plants will grow on potato plants and 

 potato plants on tomato plants. When 

 the potato is the root, both tomatoes and 

 potatoes may be produced ; when the to- 

 mato is the root, neither potatoes nor 

 tomatoes will be produced. Chestnut will 

 grow on some kinds of oak. 



71. The forming, growing tissue of the 

 stem (on the plants we have been dis- 

 cussing) is the cambium, lying on the out- 

 side of the woody cylinder, beneath the 

 hark. In order that union may take place, 

 the cambium of the cion and of the stock 

 must come together. Therefore the cion 

 is set in the side of the stock. There are 

 many ways of shaping the cion and of 

 preparing the stock to receive it, These ways are dictated 

 largely by the relative sizes of cion and stock, although 

 many of them are matters of mere personal preference. 

 The underlying principles are two : securing close con- 

 tact between the cambiums of cion and stock ; covering 

 the wounded surfaces to prevent evaporation and to 

 protect the parts from disease. 



72. On large stocks the commonest form of grafting is 

 the cleft-graft. The stock is cut off and split; and in one 

 or both sides a wedge-shaped cion is firmly inserted. 

 Fig. 39 shows the cion; Fig. 40, the cions set in the stock; 

 Fig. 41, the stock waxed. It will be seen that the lower 



38. Currant catting. 



