16 • MUTATIVE Ri:VERS10NS IX COTTON. 



AGRICULTURAL SIGNIFICANCE OF REVERSIONS. 



If the Hindi characteristics continue to reassert themselves in the 

 Egyptian cotton, complete reversion is a less serious ohstacle to com- 

 mercial uniformity than partial reversion. It is much easier to recog- 

 nize and destroy the complete Hindi plants than the intermediate 

 individuals that give only slight expressions of the Hindi character- 

 istics. 



In plantings of the superior Jannovitch and Xubari varieties the 

 proportion of the complete Hindi reversions has exceeded that of the 

 plants that show an intermediate or partial expression of the Hindi 

 characters. This is in notable contrast'with the behavior of a planting 

 of the older and less improved Ashmuni variety, where a large pro- 

 portion of the plants show some of the Hindi characters. Whether 

 these differences should be ascribed to the more careful breeding of 

 the Jaimovitch and Nubari varieties or to the different conditions of 

 the fields is not certain. It may be that the intermediate plants 

 represent new or relativelj^ recent crosses between the Hindi and 

 Egyptian forms of plants, rather than partial reversions, but the 

 large numbers of plants that show Hindi seed characters indicate a 

 very general presence of Hindi tendencies, at least in the Ashmuni 

 stock. In any case, the recognition of the complete reversions will 

 assist the careful planter in learning to detect the Hindi characteris- 

 tics, even in their less conspicuous degrees of expression. 



Hybrids and extreme forms of reversions are not the only types of 

 deterioration that must be guarded against if the need of a high degree 

 of uniformity is to be met. Many plants that do not depart from the 

 Egyptian characteristics will be found to fall far below the standards 

 of an improved variety, either in fertility or in the qualities of the 

 lint. There is no reason to suppose that uniformity can be main- 

 tained without continued selection in an}^ field crop grown from seed." 



If reversions were to be looked upon as ordinary hybrids like those 

 that result from recent crossing, it would appear impracticable to 

 guard the crop from contamination, and hence impossible to obtain a 

 uniform commercial product. No matter how carefully the fields of 

 the Egyptian cotton may be isolated, variations may still occur that 

 can easily be mistaken for hybrids. The difficulty of securing ade- 

 quate isolation of the Egyptian cotton will be serious enough in any 

 regions where Upland cotton is grown, but it need not be exaggerated 

 by the condemnation of stocks that may continue to show reversions 

 without recent contamination. 



The occurrence of reversions in one locality or in one season need 

 not stand in the way of early return to practical uniformity if an 



a Local Adjustment of Cotton Varieties. Bulletin 159 Bureau of Plant Industry, 

 U. S. Dept. of Agriculture, 1909, pp. 56-G2. 

 [Cir. 53] 



