A STUDY OF HYBEIDS IN EGYPTIAN COTTON 



THOMAS H. KEARNEY and WALTON G. WELLS 

 Bureau of Plant Industry, United States Department oi 



Inteoduction 

 The Egyptian type of cotton comprises ] 

 rieties which have presumably originated by mutation 

 (Kearney, 1914). This presumption is based upon the 

 following facts : 



1. Each variety descended from a single individual 

 which differed in several characters from the parent 

 form. 



2. The absence or extreme rarity of connecting forms 

 and the infrequency of sterility in both the parental and 

 the mutant stock make it difficult to account for these 

 mutants on the basis of recombination, as ordinarily 

 understood. 



3. The new characters of the mutant are uniformly ex- 

 pressed in the successive generations of its offspring as 

 long as hybridization with other forms is excluded. 



The observed facts make it difficult to escape the con- 

 clusion that these mutants are the result of simultaneous 

 alteration of several factors in the egg cell after fertiliza- 

 tion. 1 Otherwise, it is necessary to assume that the mu- 

 tant has resulted from the union of a male and a female 

 gamete, in both of which similar but independent altera- 

 tion had taken place with respect to several factors. 

 Probability is so greatly against this interpretation as to 

 make it almost unthinkable. 



The question suggests itself, what are the conditions 

 under which mutation occurs in Egyptian cotton? The 

 appearance of mutants has thus far been observed only 

 in mixed stocks (Kearney, 1918, pp. 60-61). Hence, not- 



