COTTON BREEDING 301 



267. Improvement of cotton seed profitable. A study 

 of the results of any tests of varieties of cotton reveals a 

 wide difference between the yields of the most productive 

 varieties and of the least productive. The difference is even 

 greater between common or unimproved cotton and the best 

 varieties. It is probably safe to estimate that a suitable 

 improved variety will, as a rule, yield at least 20 per cent 

 more lint per acre than will unimproved or scrub cotton. 



268. Crossing vs. selection as a means of improving cot- 

 ton. In improving cotton or any other plant, reliance 

 is placed on selection or on hybridizing, or on a combina- 

 tion of both of these processes. Selection attains the quick- 

 est results, especially if a beginning be made with an es- 

 tablished variety. Selection is the only process that farm- 

 ers, as a rule, need to practice. 



Crossing of two widely different individuals or varieties 

 is sometimes performed in the hope of uniting in the off- 

 spring the good qualities of both. The chances are much 

 against securing this desired combination in the majority 

 of the plants of the progeny ; even when the combination 

 is secured in one plant, it is not inherited by the majority 

 of its offspring. 



After a cross is made, the plants grown from such crossed 

 seed must be carefully selected for a number of years 

 before there is much uniformity between the different 

 plants. One need scarcely expect the type to become well 

 fixed in less than five years after making the cross. There- 

 fore, crossing is scarcely practicable for most farmers; 

 but it can be used to a limited extent by a plant-breeder, 

 that is, by one who devotes a large proportion of his time 

 to the improvement of plants. 



