THE LIFE CYCLE 



361 



the cambium or growth layer of scion and stock into close 



contact, and 2) protection of the cut surfaces from evapora- 



tion and from the weather. 



Such combinations of the 

 higher plants are possible only 

 between rather closely related 

 forms (usually, between 

 members of the same genus), 

 and every species has its com- 

 bination preferences, which 

 can only be learned by trial. 

 Pear cions, for example, will 

 grow well on quince stocks, but 

 quince cions will not thrive on 

 the pear. Potato and tomato 

 will thrive in either combina- 

 tion, and when the tomato is 

 the cion, both potatoes and 



tomatoes may be produced on one plant (fig. 211). 



At its best the union is mainly a co-adjustment of trans- 



portation systems, admitting of interchange of food mater- 



rials; each part retains its own in- 



dividuality, and, the results of the 



combination are not heritable. The 



objects of grafting are mainly two: 

 i. To combine the characters of 



two species in one individual. 



Thus, in order, to add to the good 



qualities of certain apples the 



hardiness of the Siberian crab, apple 



cions are grown on crab stock. In order 



to adapt certain plums to southern 



soils, plum cions are grown on peach 



stock. When the vineards of France 



FIG. 210. Grafting methods with 

 plants, a, splice grafting; b, cleft 

 grafting; c, bud grafting (or more 

 commonly called budding), u, u,u, 

 u, M, cions. v, v, v, v, stocks. 

 The second figure of the cleft graft 

 shows how the grafting wax is 

 applied to cover the wound. 



Fl e 2 p \ ant $% b y 

 " ci n 



