344 PLANT AND ANIMAL BREEDING 



improvement of food-producing plants and animals. The cattle 

 of the Middle Ages were about the size of the average calf of to-day, 

 but through many generations of selective breeding the size of 

 cattle and their yield of milk have been increased to a remarkable 

 degree. 



Alfalfa is especially hardy. It withstands droughts, and it may 

 yield as many as nine cuttings a season. Due to. careful selection 

 of seeds and cultivation of the ground a field of alfalfa will furnish 

 sufficient food for three to six times the number of cattle which 

 it formerly supported. Plant breeders have been able to increase 

 the amount of sugar in beets so that the number of pounds of beets 

 needed to make one pound of sugar has decreased from eighteen 

 pounds in 1836 to seven pounds in 1904. Luther Burbank im- 

 proved the potato by making it resistant to a disease called the 

 potato blight, and by increasing its starch content. It is said, 

 that this species of potato adds seventeen and one half million 

 dollars to the farm incomes each year. 



One of the best dairy cows of recent years, gave 20,616 pounds 

 of milk and 1005.9 pounds of butter fat in one year. She gave 

 more than her weight in milk each month. Contrast this cow with 

 a prize cow of 1904, that gave 567 pounds of butter fat in one 

 year. 



Every day our agricultural experiment experts and other scien- 

 tists are improving our foods. These products are not produced 

 in a haphazard way. They are frequently the results of careful 

 experimental breeding. It is, however, only within the last 

 twenty-five years that sufficient knowledge of the laws of heredity 

 has been available to put plant and animal breeding on a scientific 

 basis. 



It is the plant breeder's concern to increase the food content of 

 grains and fruits, to produce new species immune to disease, to make 

 certain varieties hardy so that they can be grown in more northern 

 climates, and to hasten maturity. The average yield per acre 



