PROBLEM 5. Breeding New Types of Aimnals and Plants 



Scion 



5O: 



Side Tongue Cleft Bud 



Fit;. 45; There are niaiiy ways of graftiivr the scion to the stuck. M'bat tissues of 

 both scion a?7d stock 7/nist be placed in contact? 



waxed. After a short time the scion gro\\ s 

 onto the stock, forming a part of the 

 rooted plant. But the genes of the scion 

 and the genes of the stock remain un- 

 changed. The\' do not mingle or affect 

 one another. When the cells of the scion 

 divide and the scion grows, ir w ill keep 

 the genes it had before it was grafted. 

 Grafting is not a method of hybridizing. 

 It is a convenient way of propagating or 

 obtaining more of a certain type of 

 plant, for the grafted scion grows larger 

 every season. If a breeder has a plant with 

 a particularly desirable combination of 

 characters he can graft many such scions 

 on other stock and be sure that the de- 

 sirable characters will continue to appear 

 in every scion. All commercial varieties 

 of fruit trees are propagated by grafting. 

 And grafting is, of course, the only 

 method by which seedless fruits can be 

 propagated. When the first scion from a 

 seedless orange tree was grafted on an 

 ordinary orange tree, the scion grew and 

 branched; twigs were again cut off and 

 grafted. Soon there were whole orchards 

 of trees bearing seedless fruits. You will 

 find Exercises 12, 13, and 14 helpful. 



Fig. 454 A pecan stock has been grafted with 

 pecan scions of a better variety. How many 

 scions were grafted? The grafts were made on 

 August 10; the lower branches {not grafted) 

 were reinoved on September i. Why were the 

 lower brajiches not removed ivhen the grafting 

 was done? Why were the lower branches ever 

 removed? (u. s. department of agriculture) 



