COTTON SELECTION ON THE FAKM. 9 



The next generation may not show the undesirable character, but 

 this does not prove that it has been completely eliminated. Our 

 present knowledge of the behavior of characters in hybrids indicates 

 that the grandchildren and later descendants of a degenerate indi- 

 vidual are more likely to show the degenerate characters than the 

 immediate offspring. Thus, in spite of all the care that may be 

 taken to reject the seed of every plant that brings undesirable char- 

 acters into expression, degenerate characters may continue to be 

 inherited for any number of generations. 



Selection as applied to an improved variety of cotton is simply a 

 means of keeping undesirable characters out of expression. One of 

 the principal objects to be gained by detailed study of heredity in 

 cotton is to learn the method of selection that keeps the undesirable 

 characters most thoroughly suppressed. 



VALUE OF EXTERNAL CHARACTERS IN SELECTING COTTON. 



By using external characters in selection it is possible to secure a 

 large measure of protection against the inheritance and subsequent 

 expression of the characters of degenerate individuals. Studies of 

 degenerate variations of several different types of cotton have shown 

 changes in the external or vegetative characters as well as in those of 

 the fruit and seed. It seldom, if ever, happens that a cotton plant 

 makes a definite change in a single character and continues to resem- 

 ble the parent variety in all other respects. Plants that are going to 

 produce bolls, or seeds, or lint different from those of the parent 

 variety usually give notice well in advance by changes in the exter- 

 nal vegetative characters. Some of the most injurious variations are 

 the easiest to throw out early in the season, if attention be given to 

 the external characters. Peculiarities of individual plants that may 

 appear to have no importance in themselves become very significant 

 for purposes of selection. 



Farmers who know their varieties well enough can detect and weed 

 out degenerate variations in the seed plat even before the plants 

 reach the flowering stage, and hence before they can contaminate the 

 other plants with inferior pollen. It is much easier to recognize and 

 reject degenerate ])lants on the basis of their external differences 

 early in the season than after the crop has matured. The general 

 characteristics of the young growing plants are much easier to see 

 than the differences that have to be detected by examining the seed 

 and combing out the lint. 



Plants that are too degenerate to blossom or produce any seed are 



not dangerous to the remainder of the variety, but most of the bad 



plants produce flowers, even if they do not ripen seed. One of the 



worst forms of degeneracy in cotton, and one that seems to be very 



49350°— Cir. 66—10 2 



