BREEDING AND SELECTION 



65 



by other pollen, the ears on such detasseled stalks are 

 better developed than the ears on the stalks not so 

 detasseled. By detasseling two rows and leaving two 

 rows with tassels, enough pollen will be provided for 

 the complete fertilization of the field. See Fig 22, 

 illustrating pollen grains greatly magnified. 



The Illinois experiment station found that by in- 

 breeding, that is, placing the pollen of the stalk upon 

 the silks of the ear on the same stalk, the size of the ear 



Pig 20— Effect of Four Years' Inbreeding 



Small row inbred; large row cross-bred 



and stalk would be eventually decreased. In other 

 words it appears as though inbreeding in corn tends to 

 develop weakness and a general deterioration of the 

 vitality of the plants. 



The crossing of varieties, however, is now known 

 to lead to beneficial results in the present varieties. 

 There seems to be enough variation in any one variety 

 to select from, and by introducing foreign character- 

 istics it becomes very difficult to fix any of them. 



