314 ESSENTIALS OF BOTANY 



Corn of the South and the Middle West, growing 

 sometimes to a height of from fifteen to twenty or more 

 feet, requires nearly or quite six months to mature, but 

 the less prolific two- or three-foot kinds grown in the 

 northern United States and Canada mature in less than 

 three months. 



394. Wheat-Breeding. — Wheat is the most important 

 grain for human food in temperate climates, and North 

 America is by far the greatest wheat-producing region in 

 the world. The annual value of the crop of the United 

 States ranges from §250,000,000 to 1500,000,000. Wheat 

 has been cultivated for so many thousands of years that its 

 origin is not perfectly known. Scientific wheat>breeding, 

 however, began hardly a century ago and has progressed 

 more in the United States since 1890 than during all our 

 previous history. 



Some desirable qualities to be sought for in wheat- 

 breeding are : 



(1) Large yield per acre. 



(2) Good quality for bread-making, requiring a high per 

 cent of the tenacious gluten, the main proteid portion of 

 the grain. 



(3) Hardiness, shown in resisting severe winter con- 

 ditions. 



(4) Resistance to rust. 



(5) Resistance to drought. 



Not all of these qualities can be combined in the highest 

 degree in anj^ one variety, and therefore every region should 

 grow the particular kind of wheat best suited to the local 

 conditions and market. 



In order to show how carefully the process of wheat- 

 breeding is managed in our best agricultural experiment 



