MUTATIVE REVERSIONS IN COTTON. 7 



the expression of cliariicters, but eoliereiice alone would not explain 

 the further fact that plants of preponderantly Egyptian ancestry 

 may depart from the Egyptian characteristics and appear as com- 

 pletely un-Egyptian Upland or Hindi. In stocks where the crossing 

 upon the Egj^ptian is limited to half-blood U])lands there is a general 

 reduction of the expression of Upland characteristics as compared 

 with the crosses of full-blood Upland upon the Egyptians, but such 

 dilutions do not preclude reversions to complete I^pland forms. 



Upland or Hindi characters that remain completelylatent or without 

 expression in one generation may recover their potency and return 

 to complete expression in some of the members of the next generation. 

 One planting of hj'brid seed may show a preponderant resemblance 

 to one parent, another ])lanting to the other parent. One planting 

 of a stock of seed may show none of the Hindi or Upland reversions, 

 while another planting of the same stock of seed or another part of the 

 same field may show very pronounced examples. Three plantings 

 of the Jannovitch variety of Egyptian cotton in 1909 showed Hindi 

 individuals of extreme form, although a large planting of the same 

 stock of seed in 1908 gave only a few aberrant individuals in which 

 comparatively slight evidences of Hindi contamination were detected." 



A question may still be raised regarding the authenticity of this 

 extreme example where complete reversions have seemed to take 

 place, as it were, by wholesale. Although there is no reason to doubt 

 the equality and general uniformity of the imported Egyptian seM, 

 it is still possible to imagine that the seed planted in 1908 was of dif- 

 ferent origin from that grown in 1909, even though .both came from 

 the same imported stock. Such possibilities as the sinking of the 

 smooth Hindi seeds to the bottom of the bag, or failure to germinate, 

 or earl}^ death of the Hindi seedlings have also to be reckoned with, 

 though the chances that such accidents could afford any complete 

 explanation of the facts appear very remote. The consistent general 

 behavior of the Egyptian plants in the different fields and experi- 

 mental plats and the general scattering of the Hindi individuals in 

 the plantings of 1909 give no support to the idea that the seed was 

 different. An absolute determination of the matter will require the 

 study of more numerous and still larger plantings of seed, mixed with 

 special thoroughness to avoid the possibility of accidental segregation 

 of any of the different qualities that may be included. 



Kegular field plantings of Egyptian cotton can be made to serve 

 the purposes of such experiments, but it is desirable to present in 

 advance the collateral evidence for expecting that reversions will 

 occur and that they are likely to appear in different numbers and 



. «■ A Study of Diversity in Egyptian Cotton. Bulletin 156, Bureau of Plant Industry, 

 U. S. Dept. of Agriculture, 1909, pp. 18-21. 

 [CIr. 53] 



