PLANT-BREEDING 337 



resistant character can be combined with good quality of 

 grain and good yield, the result will be of very great impor- 

 tance. This work is under progress, but the results have not 

 been announced. 



These illustrations from wheat and corn, our two most im- 

 portant cereal crops, indicate the possibility of breeding 

 drought-resistant races of all the important cultivated plants. 



42. Corn-breeding. It would not be fair to give the 

 impression that plant-breeding is a simple problem and that 

 all plants can be handled alike. The breeding of corn will 

 serve to illustrate how difficult the problem often is. A great 

 deal of corn-breeding has been done, and it is still one of our 

 most important problems, for corn is not only one of our most 

 important cereals, but it is probably the most difficult one 

 for the plant-breeder to handle. The ordinary field of corn 

 is a remarkable mixture of different kinds of individuals, so 

 that ordinary mass culture reaches very indefinite results. 

 The discovery that the best method of selection is to select 

 the best ears rather than merely the most vigorous individuals 

 has resulted in a very largely increased yield. One difficulty 

 in connection with corn, however, is that pollination is so 

 free that under ordinary conditions it is beyond control. 

 During the four or five days when a young ear is being pol- 

 linated, the pollen is flying freely from the tassels of many 

 plants, so that some of the kernels of an ear may have received 

 undesirable pollen. Therefore, after a good ear has been 

 selected for seed, it may contain undesirable hybrid kernels. 

 This means that selection must be continuous, not only to 

 secure desirable individuals, but also to weed out undesirable 

 hybrids. It is obvious that in this case pedigree culture 

 deals with pedigrees known on the female (ear) side and only 

 vaguely known on the male (tassel) side. 



When rigid pedigree culture is applied to corn, so that pol- 

 lination is accomplished under control, and a pure strain is 

 secured, free from all mixture with other kinds of individuals, 



