MUTATIVE REVERSIONS IN COTTON. 17 



iuloquate selection is maintained and favorable conditions are pro- 

 vided. Familiarity with the vegetative characters of the plants will 

 enable the undesirable reversions to be rogued out before the time of 

 flowering, so that crossing with such plants may be avoided. Tend- 

 encies to variation that are shown in the lint and the seeds can be 

 rejected when the necessar}" selections are made in the fall to secure 

 liigh-grade seed for the next season's planting. The influence of the 

 external conditions upon reversions is only one of many indications 

 that the uniformity of the crop, as well as the yield of fiber, will de- 

 pend upon cultural methods as well as upon the seed that is planted. 



CONCLUSIONS. 



The phenomena of reversion in cotton are not confined to the changes 

 of single characters, but may result in wide departures from parental 

 types and bring different series of varietal characters into expression. 



The return of ancestral characters to expression does not depend 

 upon recent hybridization, but may be shown in abrupt, mutative 

 variations of '"pure-bred" stocks that have been selected for the uni- 

 form expression of a single set of characters. 



Reversions may be aroused by new or unfavorable conditions of 

 environment and may vary in extent and frequency with changes of 

 external conditions. The uniformity of a stock in one place affords 

 no assurance that diversity will not reappear in another locaHty. 

 Diverse characteristics continue to be transmitted and may return 

 to expression after many generations. 



The variations of the different types of cotton have general simi- 

 larities and may be arranged in parallel series. The general range 

 of the ancestral diversities of cotton is also to be learned from the 

 study of wild or unimproved types and from the diversities that in- 

 terfere \nth the Mendelian expression of characters in hybrids. 



The uniformity of the progeny of mutative variations renders them 

 greatly superior to Iiybrids for breeding purposes. The possibility 

 of obtaining superior mutative reversions from later generations of 

 dilute hybrid stocks is worthy of investigation, especially in cases 

 where desirable Mendelian combinations are not obtained in the earher 

 generations of hybrids. 



The Hindi variations of the Egyptian are similar in their characters 

 and behavior to some of the reversions that appear in Upland varie- 

 ties and may prove to be forms of reversion rather than results of 

 recent contamination with a distinct type of cotton. 



The more pronounced forms of reversion in Upland cotton, like the 

 Hindi variations of the P^^gyptian cotton, are readily distinguished by 

 vegetative characters, so that they can be rogued out before the time 



[Cir. 53] 



