CHAPTER III 



PRINCIPLES OF PLANT BREEDING 



The vast possibilities of plant breeding can hardly be estimated . . . 

 They are not for one year nor for our own time and race, but they are benefi- 

 cent legacies for every man, woman, or child who shall ever inhabit the earth. 



LUTHER BURBANK. 



BREEDING of cultivated plants or domestic animals is their 

 systematic raising or reproduction under the direction of the 

 expert for the purpose of securing improved forms. The object 

 may be to increase the profits or merely for scientific experiment. 

 When desirable traits or characters are noticeable in certain 

 individuals or types, a trial may be made to determine whether 

 or not those points will be reproduced or perhaps intensified in 

 the offspring. 



Heredity. This is one of the laws of nature which governs 

 the work in scientific breeding. The law of heredity is that all 

 plants and animals inherit from their ancestors certain charac- 

 teristics, forms, qualities, etc. "Like produces like," or "similar 

 produces similar," are true of both plants and animals. The 

 undesirable characteristics are just as certain to be transmitted 

 as the more desirable ones. The law is not absolute. It is subject 

 to some variation due to environment or other causes. 



Variation. There is a natural tendency in nature for all 

 creatures to differ from each other and from their parents. It 

 may almost be said that no two trees in a nursery row are exactly 

 alike, or that no two plants in a bed of seedlings are alike (Fig. 

 16). This tendency of varying from each other and from their 

 parents is even more noticeable among animals. It allows the 

 scientific breeder to select the desired types and produce from 

 them, in time, those valuable for special purposes. 



Mutation or extreme sudden variations from the type are 

 sometimes noticeable. These may be called "sports.'' It is 

 believed by some scientists, De Vries and others, that the extreme 

 characteristics of mutation or sports may be transmitted to suc- 

 ceeding generations. Others believe that plants do not have the 

 power to transmit these. It is certain that the offspring often 

 revert to the original type. The breeders of plants and animals 

 22 



