CHAPTER IV 



APPLICATION OF PRINCIPLES TO FARM CROPS 



Still will the seeds, though chosen with toilsome pains, 



Degenerate, if man's industrious hand 



Cull not each year the largest and the best. VERGIL. 



THE principles of breeding have only recently been applied to 

 field crops. Some more or less careful selection has been exercised 

 for many years. Man has searched the world over for natural 

 varieties and strains, but in many cases has failed to keep them 

 pure or to improve them by continued selection. Crossing, break- 

 ing the types and establishing new varieties is now much more 

 common among scientific breeders of plants. The New York 

 College of Agriculture is establishing a new strain of timothy. 

 The Minnesota Station and the Kansas Station have established 

 new and valuable strains of wheat. Many scientific breeders have 

 worked upon corn. It is an easy subject to work upon, and gives 

 striking results. Cotton and tobacco have been improved and 

 valuable varieties of each established by the work of several 

 southern states. Experiment stations have done much to improve 

 the yield and quality of Irish potatoes (Figs. 23 and 24). Sugar 

 beets were greatly improved by careful selection during the Napo- 

 leonic wars. Prizes were offered by Napoleon for any variety yield- 

 ing a high percentage content of sugar. Commercial plant breeding 

 is successfully conducted on seed farms in America and in Europe. 



Self-Pollinated Plants. The methods employed in the im- 

 provement of wheat, oats and other self-pollinated plants are very 

 different from those used where the pollen may be carried from one 

 plant to another. The chief work in the breeding of wheat or 

 oats is to study the yield of individual plants. The seed from 

 different plants is kept intact by covering the heads with cloth, 

 as shown in figure 25. This keeps the birds away and prevents 

 the shelling of the seed. The plants yielding the most and best 

 seed are kept separate from the others. The seed may be planted 

 in separate rows or plots without danger of mixing with the others. 

 The yield of individual plants or rows is again recorded. By such 

 careful selection the improvement may go on for many generations 

 (see Fig. 26). 

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