Nos. 622-623] HYBRIDS IN EGYPTIAN COTTON 



501 



Correlation of Characters 



It was sought to ascertain whether these hybrids show 

 genetic as distinguished from merely physical or physio- 

 logical correlations, in other words, whether there is co- 

 herence in the transmission of the parental characters. 

 To this end, application was made of the test proposed 

 by Collins (1916, p. 439), i. e., comparison of the coeffi- 

 cients of correlation of the F 2 with those of the Fj. It 

 is assumed that if the F 2 coefficient significantly , - 

 that of the F^ in the direction indicated by the relation 

 of the parental means for the two characters, genetic 

 correlation or coherence of characters is indicated. For 

 example, the Pima parent has a lower leaf index and a 

 higher boll index than the Gila parent. If there is co- 

 herence of these characters, the hybrid should show a 

 negative correlation and the coefficient of correlation 

 should be significantly larger in the F 2 than in the F r 



The coefficients of correlation of 40 pairs of characters 

 were determined for both the F x (grown in 1915) and F 2 

 (grown in 1916), upon the basis of one measurement of 

 each character on each plant. 8 In three of these cases 

 the coefficient of correlation of the F 2 was significantly 

 larger than that of the F 1 (difference from 3.5 to 4.5 

 times its probable error), in the direction indicated by 

 the parental relation. Since, however, the coefficients of 

 correlation of the first generation (1915) and second gen- 

 eration (1916) of the parental progenies had also been 

 found to differ in magnitude, the possibility was consid- 

 ered that the difference in the F x and F 2 hybrid coeffi- 

 cients was at least partly due to variations in the weather 

 of the two years. The coefficients of correlation for the 

 three character pairs above mentioned were therefore 

 calculated for a new F, which was grown in the same 

 vp 3 r as the F„. 9 When the F., and the new F, coeffirients 



