Nos. 622-623] HYBRIDS IN EGYPTIAN COTTON 



by the Bureau of Plant Industry in cooperation with the 

 Indian Service. The writers are indebted to Mr. G. N. 

 Collins of the Bureau of Plant Industry for many help- 

 ful suggestions throughout the course of the investiga- 

 tion. 3 



Plan of the Investigation 

 The only varieties of Egyptian cotton of which ap- 

 proximately pure strains were available when the experi- 

 ment was begun were the Yuma, Gila and Pima varieties, 

 all of which had been developed in Arizona. These va- 

 rieties were described (with illustrations of the leaves, 

 bracts, and bolls) and an account of their origin was 

 given in an earlier publication (Kearney, 1914). Their 

 relationship may be indicated thus : 



The Gila and Pima varieties were chosen because they 

 show the greatest amount of difference in the largest 

 number of characters. Of the three varieties, Grila is 

 most similar to the common ancestor, Mit AM, and Pima 

 is the most distinct from it. Gila may, in fact, be re- 

 garded as representing a small portion of the area of 

 variation of the extremely heterozygous Mit Afifi stock 

 from which all these varieties have descended, while the 

 characters of Pima are far outside the hitherto observed 

 range of variation in Mit Afifi. The hybrids described 

 in this paper may therefore be taken to represent, in a 

 measure, the result of crossing the mutant Pima with its 

 more remote ancestor, Mit Afifi. 



Several typical individuals of each variety were se- 

 lected in July, 1914 A number of flowers were self- 

 pollinated on each plant and interparietal cross-pollina- 

 tions were made among them. The resulting first gen- 



