496 THE AMERICAN NATURALIST [Vol. LIT 



ond generation progenies of the plants selected as par- 

 ents of the hybrids, showed overlapping ranges for all 

 characters excepting fuzziness of the seed and color of 

 the fiber. These two characters were measured on only 

 small numbers and overlapping would very likely have 

 been observed if larger populations had been compared. 



The Simple Hybrids 

 Means 



Comparing the means of the simple hybrids (Pima X 

 Uila ) with those of the parents, a strong tendency to in- 

 termediacy was apparent. The means for a large ma- 

 jority of the characters, in both the F 1 and F 2 , lay be- 

 tween the parental means, and in nearly one half of the 

 total number of characters the hybrid means did not 

 differ significantly from the midpoint of the parental 

 means. The relative number of characters for which 

 the departure of the hybrid mean was towards the Pima 

 mean was much greater in the F x than in the F 2 . This 

 was probably due to increased vigor in the conjugate 

 generation, eight of the thirteen characters which showed 

 a significant 5 departure of the hybrid F x mean from the 

 midpoint of the parents being size characters for which 

 the Pima parent gave a larger mean than the Gila parent. 



Eleven F 3 progenies of the simple hybrid were grown 

 in 1917 from plants which were selected in the F 2 in 1916 

 because of their approach to one or the other parent or 

 because of their intermediacy with respect to various 

 characters, especially leaf index and boll index. The F 3 

 means for these characters in all cases fell between the 

 means of the third generation parental progenies, or 

 else did not differ significantly from the mean of one or 

 the other parent. 



Coefficients of Variation 

 In all three generations the hybrids gave significantly 

 larger coefficients of variation, for most of the characters, 



amount" ffer r C th 0r ? here refem?tl to as "significant" when 



