SOME PRINCIPLES OF PLANT BREEDING 497 



circumference of ear, shape of ear and cob, number of kernels in 

 a row and number of rows, size and shape of kernels, weight and 

 color of grain and cob. White corn meal is preferred by some 

 for domestic use and is almost exclusively used in the south; 

 some in the north and northwest prefer the yellow meal. This 

 preference in some cases is probably due to custom. Attention 

 should also be given to developing in harmony with this an all 

 round good plant, and to yield per acre. In every field of com- 

 mon corn there are stalks w r hich do not bear ripe ears, i.e., are 

 " barren." These often produce more pollen than fertile plants 

 and exercise a great influence in pollinating the fertile ears. In 

 selection all such stalks should be removed before the pollen ma- 

 tures in order that this character may not be carried over into the 

 seed. Races are bred which produce a single large ear on a stalk. 

 These are more valuable when corn is husked by hand. When 

 it is husked by machinery to feed to cattle, races with several 

 small ears to each stalk are preferred. Races and varieties are 

 also bred which are more suitable to soil or climatic conditions, 

 and varieties have been developed which range from the tropics 

 to the Lake Superior region. 



667. In Minnesota wheats have been bred to increase the 

 number of bushels per acre, the famous " Minnesota No. 169 " 

 producing three to five bushels more per acre than the ordinary 

 wheats. When grown largely over the state it showed an aver- 

 age yield of 18 per cent over the common wheats. The gradual 

 development of these improved races of different cultivated 

 plants and their general cultivation in place of the common sorts 

 will add many millions of dollars to the value of our crops with 

 no additional cost in the production. 



II. THE PRODUCTION OF NEW VARIETIES. 



668. Variation increased by cultivation, by better food 

 supply and by crossing. It is well known that cultivation and 

 an increased food supply make plants more variable than they 

 are in the wild state. The plant breeder seizes upon this and 



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