MAN'S CONQUEST OF NATURE 573 



have already been found, it is a very serious enemy of the wheat 

 crop. Fortunately, in the epidemic of 1935 a new spring wheat, 

 the Thatcher, developed by the Minnesota Agricultural Experiment 

 Station in co-operation with the United States Department of Agri- 

 culture, proved resistant to all known strains of rust. 



A recent exhibition in the Department of Agriculture displayed 

 about 150 new superior varieties of field crops. No less than eight su- 

 perior wheats, among them Turkey, Thatcher, Marquis, and Kanred, 

 with several new varieties of oats and barley, are now cultivated on 

 more than 40 million acres of crop land each year. New varieties 

 of potatoes, such as the Katahdin, resist some of the serious diseases 

 of potatoes. Peas and melons unaffected by parasitic wilt have 

 been developed, while fruits of superior color, appearance, and keep- 

 ing quality have been evolved. 



In livestock, animals have been produced that show greater resist- 

 ance to disease, larger body size, better growth, better performance, 

 and greater fecundity. In breeding these animals, it has been found 

 that, through a use of Mendel's laws, certain of these characteristics 

 are shown to breed true, since they are alike in both parents. An 

 outstanding successful strain of cattle, known as the Santa Gertrudis, 

 has been recently developed in Texas. The Department of Agricul- 

 ture is now experimenting with crosses of Brahman and Aberdeen- 

 Angus breeds of cattle to establish certain desirable characteristics. 

 A new strain of sheep known as the "Columbia type," which is 

 particularly adapted to the rather rigorous regions of the Northwest, 

 has been developed from the Rambouillet and Lincoln breeds of 

 sheep. Crosses of poultry have been bred which produce as many as 

 300 eggs per hen per year, as against less than 100 eggs from the 

 average hen. At some state experiment stations certain cows of su- 

 perior breeds have been found to produce as much as 1000 pounds 

 of butterfat per year, while the average cow produces little more 

 than 200 pounds per year. These are only a few of the accomplish- 

 ments brought about by practical breeding experiments in this 

 country. 



Economic Values of Plants and Animals 



The results of this gradual domestication of plants and animals are 

 seen today in the very great value of our agricultural products and 

 farms. According to census reports the value of farm property in 

 the United States, in spite of the long period of depression, is more than 



