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 $500,000,000. 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. 
(8) 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 any 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 
