Nos. 622-623] HYBRIDS IN EGYPTIAN COTTON 



495 



Characters Measured and Significance of the Varietal 

 Differences 



The Pima and Gila varieties, as represented by the 

 first and second generation progenies of the selected par- 

 ent individuals, differed by an amount equal to three or 

 more times the probable error of the difference, in re- 

 spect to 24 characters. Many of these are physically or 

 physiologically correlated, but six of the characters 

 showed practically no correlation inter se, in either 

 parent. Most of these characters are expressions of 

 size (e. g., the length of the internodes, leaves, floral 

 parts, bolls and fiber) or are ratios between two size 

 characters and expressive of shape. The leaf index 



^f^rX iOO an d the boll index f en g th x 1 00 showed 

 width diameter 

 especially significant differences between the two varie- 

 ties named, the difference in the second generation hav- 

 ing been 26 times the probable error in respect to leaf 

 index and 46 times the probable error in respect to boll 

 index. In length of fiber .the difference between the 

 parents in the second generation was 22 times its prob- 

 able error. The only characters of diagnostic value 

 which could not be accurately measured and which were 

 therefore determined by grading, were color of the fiber, 4 

 amount of fuzz on the seeds and roughness of the boll 

 surface (depending upon the depth, number and regu- 

 larity of distribution of the pits in which the oil glands 

 are situated). Even in respect to these characters the 

 differences were of degree rather than of kind. 



The Gila variety, as represented by three successive 

 selfed generations of the progenies of the parent plants, 

 gave larger coefficients of variation for most of the char- 

 acters than did the Pima variety. Since no general de- 

 crease in the variability of either variety was observed 

 after three generations of selfing, it would appear that 

 Gila is inherently more variable than Pima. 



The two varieties, as represented by the first and sec- 



