CHAPTER XXIII 

 PLANT BREEDING 



377. What is plant breeding? Plant breeding means the 

 intentional production and perpetuation of new and especially 

 desired varieties of plants. As a science it is not much more 

 than fifty years old. But some plants have been cultivated for 

 over forty-five centuries, 1 and during all that time more or 

 less attention has been paid to choosing and keeping up desir- 

 able varieties of plants. 



378. Selection of spontaneous varieties. Plants in a state of 

 nature produce many varieties by ordinary variation, and they 

 may occasionally produce new species by the kind of extensive 

 and abrupt change which is known as mutation. 



Only a very few of all the multitude of spontaneous vari- 

 ations among plants are likely to be valuable to man. An 

 example of this is afforded by the results obtained by the 

 discoverer of the Concord grape. This familiar grape was a 

 seedling from a rather promising wild variety. The original 

 Concord grape is so valuable on account of its productiveness 

 and hardiness and the size of its fruit that it has been dissem- 

 inated by cuttings over a large part of the United States and 

 portions of Europe. The annual world's crop of this variety 

 is now exceedingly large. The grower of the Concord mother 

 vine raised more than 22,000 seedlings from Concord seeds, 

 and found only 21 of these worthy of further trial. Not one 

 of these seedlings is now a well-known grape. 



Most farm crops afford many variations in the same field. 

 These variations do not show themselves merely in slight mat- 

 ters of proportion or size of organs, details interesting only 

 to the botanist ; they may greatly affect the economic value of 



1 See De Candolle, Origin of Cultivated Plants, chap. i. 

 412 



