STRUCTURE OF THE STEM 75 
90. Grafting. — When the cambium layer of any vigor- 
ously growing stem is brought in contact with this faves 
in another stem of the same kind or 
a closely similar kind of plant, the two 
may grow together to form a single 
stem or branch. This process is called 
grafting, and is much resorted to in 
order to secure apples, pears, etc., 
of any desired kind (Fig. 46). A 
twig known as the scion from a tree 
of the chosen variety is grafted on to 
any kind of tree of the same species 
known as the stock, and the result- 
ing stems will bear the wished-for 
kind of fruit. Often one species is 
grafted on another, as the pear on the 
quince or the apple. Rarely trees dif- 
fering as much as the chestnut and the 
oak may be grafted together. Some- 
times grafting comes about naturally 
by the branches of a tree chafing 
Fic. 46. Grafting. 
At the left scion and stock 
: are shown ready to be 
against one another until the bark united; at the right they 
are joined and ready to 
is worn away and the cambium layer 2. with Satine wi, 
of each is in contact with that of the | 
other, or two separate trees may be joined by natural 
grafting. 
