24 RELATION OF DROUGHT TO WEEVIL RESISTANCE IN COTTON. 



higher requirement of uniformity limits the production of long- 

 staple cotton to districts where the soil moisture is adequate or is 

 supplemented by irrigation. The irrigation facilities being devel- 

 oped in many localities in southern Texas may make it possible to 

 extend the cultivation of long-staple varieties to a new region. 



It remains to be seen whether cotton-growing communities can be 

 organized to take full advantage of early long-staple varieties that 

 have been developed. The size of the crop and the uniformity of 

 the product may both be increased if whole communities, instead of 

 scattered individual planters, can devote their time to the production 

 of long-staple varieties. The preservation of the necessary uni- 

 formity of the long-staple varieties will become much easier if no 

 short-staple types of cotton are grown in long-staple communities. 

 The deterioration of varieties through cross- fertilization in the field 

 and by the mixing of seed at gins can both be avoided in well- 

 organized communities that limit themselves to one superior variety 

 of cotton. 



DIFFICULTY OF DIRECT TESTS OF WEEVIL RESISTANCE. 



One of the chief obstacles in the study and general application 

 of the factors of weevil resistance lies in the great difficulty of making 

 any comparative tests that will definitely determine the actual 

 values even of factors that have obvious practical importance. It 

 is not reasonable to disregard these factors because of the difficulties 

 of testing them. Fortunately there is no possible conflict between the 

 cultural methods that are advised for purposes of weevil resistance 

 and those that are calculated to secure maximum production, even 

 without weevils. 



In the case of early and late varieties the planting of the two side 

 by side is likely to give an exaggerated idea of the benefits of earli- 

 ness. It is certainly to be expected that a row of late cotton will suffer 

 much more by being planted next to ah early row infested with 

 weevils than if there were no early cotton in the neighborhood. But 

 if the plantings are made in separate fields to avoid the danger of 

 weevils from adjacent rows, the equality of other experimental con- 

 ditions can not be assured. Differences of yields at the end of the 

 season can not be ascribed with any confidence to weevil differences 

 alone. The soil may differ in fertility or in the content of moisture 

 and cause wide fluctuations of the crop, even in regions that have no 

 weevils. All other considerations are likely to be overshadowed and 

 forgotton when the weevils are at hand. Nor does the use of isolated 

 fields give any assurance of equality in the numbers of weevils. Even 

 in parts of the same field the extent of damage from weevils usually 

 shows wide variations, often 50 per cent and upward, especially in 



220 



