352 PLANT AND ANIMAL BREEDING 



Artificial selection. Many experiments in breeding start with 

 hybridization, but they would be of little value unless the indi- 

 viduals showing undesirable traits were disregarded and only those 

 showing the desirable characters kept for breeding. This is called 

 artificial selection. Even so, the organisms showing the useful 

 traits will oftentimes not breed true as they are hybrids. To be 

 successful and establish the desirable qualities, large numbers of 

 matings must be tried out and only those that breed true should be 

 retained. As has been said before, when vegetative propagation 

 is possible, it is a certain means of breeding the plant true to type. 

 Improved kinds of fruit trees are propagated only by grafting. 



Method of plant propagation. The typical method of plant 

 propagation was that used by Burbank. The flowers which are to 

 furnish the pollen are carefully gathered a day or so beforehand. 

 The pollen is sifted from the flowers and kept in a cool place. The 

 tree to which the pollen is to be applied is deprived of most of its 

 blossoms in order that the remainder may be sure to develop and 

 that there may not be too many to be properly looked after. The 

 buds of the remaining blossoms are prepared for artificial pollina- 

 tion by cutting away the petals and the .attached stamens. The 

 pistils and stigmas are left uninjured and are protected from in- 

 sects. Since there are no brightly colored petals to attract them, or 

 anything for them to hold on to when entering, bees seldom ap- 

 proach these flowers. If there is any danger of insects visiting 



the flowers, a paper bag is fre- 



-pccrents ^ J. quently tied over each individ- 



mil flower. When the pistil 

 ripens, the pollen is applied by 

 dipping brush or finger into 

 this yellow powder and touch- 



i n g the stigmas. All of the 

 develop from 



The size, flavor, and quality of plums have been . . . , 



improved through selection and cultivation. tlie iruit Ol the pistil tnUS 



