Nos. 622-623] HYBRIDS IN EGYPTIAN COTTON 505 



new characters was detected in any of these progenies, 

 but since mutants in Egyptian cotton are comparatively 

 rare, it will doubtless be necessary to examine much 

 larger populations before definite conclusions can be 

 drawn as to the occurrence of mutation in these stocks. 



The principal interest of the data thus far obtained 

 attaches to the behavior of hybrids between varieties be- 

 longing to the same general type, as compared with that 

 of the hybrids between different species of Gossypium, 

 which have hitherto been the principal subject of genetic 

 investigation in this group of plants. 



The varieties used in this investigation are distin- 

 guished chiefly by size and shape characters, although a 

 few of the characters in which they differ significantly 

 have been found to behave as allelomorphs in hybrids be- 

 tween less nearly related forms of Gossypium. The 

 Pima X Grila hybrids, however, showed no evidence of 

 segregation in definite ratios in respect to any of the 

 characters measured. There was little or no evidence of 

 dominance in the F lf and the F 2 distributions were prac- 

 tically without exception unimodal. The means of the 

 simple hybrid were in most cases intermediate between 

 those of the parents. The result of twice back-crossing 

 the simple hybrid upon either parent was to obliterate 

 the expression of the characters of the other parent. 



It could not be demonstrated that genetic correlation 

 or coherence of characters occurs in these hybrids. Ap- 

 parently all characters which are not correlated physi- 

 cally or physiologically are transmitted independently. 



The second and third generations of the hybrids, as 

 compared with the parents after two and three genera- 

 tions of selfing, were not more variable than Gila, and 

 were only a little more variable than Pima. This fact 

 is of practical importance in cotton breeding, since it 

 points to the possibility of obtaining relatively stable 

 and uniform recombinations of the desirable characters 

 of varieties belonging to the same general type, although 

 breeders have found this to be well nigh impossible in 



