106 COLLEGE BOTANY 



the only way they can be propagated with any assurance of 

 securing the desired result is by means of some one of the 

 non-sexual methods. The apples and peaches do not " come true 

 to seed " ; that is, the new plants grown from the seeds produce 

 fruits quite different from the parents. Therefore, in order to 

 perpetuate a desirable fruit, it is necessary to graft or bud scions 

 of the desirable plant onto strong stocks. 



In the great majority of cases the new plants are produced 

 from stems, but in some cases new plants are produced from 

 roots. The sweet potato is a good illustration of a plant in which 

 the stems are produced from roots. In the growing of this very 

 important crop the roots are layered in especially prepared beds, 

 and produce great numbers of plants, which are pulled and set 

 in the field. Many trees, such as the plums and poplars, produce 

 shoots or sprouts from the roots. 



Variations. It is said that nature produces nc two individu- 

 als that are exactly alike; sometimes the variations are so slight 

 as to be almost imperceptible, while in other cases they are very 

 pronounced. These variations may occur in any part of the 

 plant ; they may involve size, form, color, chemical composition 

 or any other character of the plant. Therefore, new types are 

 constantly arising in every generation. Most of them are very 

 unstable, and therefore disappear in the next generation. This 

 is especially true of many of our fruits, such as the apple and the 

 peach, which are extremely variable. Fortunately the valuable 

 varieties of orchard fruits that arise in this manner can be per- 

 petuated by budding and grafting. 



Mutations. Sometimes variations are produced which come 

 quite true from the seed ; they are known as mutants. Many hor- 

 ticultural varieties of fruits, vegetables and grains have 



