A PLANT INDUSTRY BASED UPON 

 MUTATION 



Varieties of Egyptian Cotton Have Arisen Largely Through Mutation — 



Possible Relation Between Mutation and Hybridity — 



Many Problems Still Left For Solution 



Thomas H. Kearney 



Physiologist in Charge, Alkali and Drought-Resistant Plant Investigations, 



Bureau of Plant Industry, U. S. Department of Agriculture 



MOST species of crop plants com- 

 prise numerous well-marked 

 varieties. Howthese have origi- 

 nated in the seed-propagated 

 crops is still, in large measure, an un- 

 solved problem. In some cases, how- 

 ever, the evidence points to origin by 

 mutation, a phenomenon analogous to 

 bud-sporting in fruit trees and other 

 vegetatively propagated plants. Muta- 

 tion manifests itself in the sudden ap- 

 pearance of an individual which differs 

 from the parent stock in one or more 

 strongly heritable characters. If this 

 individual "breeds true," the new 

 characters being uniformly expressed 

 in its progeny generation after genera- 

 tion, a stable new variety will have been 

 produced. 



MUTATION HARD TO EXPLAIN 



Certain geneticists have endeavored 

 to explain mutation on the basis of 

 Mendelian recombination. It .tnust be 

 admitted that in the familiar .case of 

 Oenothera, for example, the .attempt 

 has not been completely su'ccessful. 

 Nor will this explanation rcover the 

 apparently well-authenticated /exam- 

 ples of mutation in asexually, propagated 

 organisms. The possibility should ,be 

 considered that mutation is not -a simple 

 but a complex phenomenon, which 

 results from different causes in different 

 groups of organisms. In Egyptian 

 cotton, the group discussed in this paper, 

 there is some evidence of a relation 



between mutation and hybridity, al- 

 though simple recombination does not 

 afford an adequate explanation of the 



facts. 



DESCRIPTION OF EGYPTIAN COTTON 



Before going further into this ques- 

 tion, it may be in order to consider 

 briefly the nature and uses of Egyptian 

 cotton and to review the plant breeding 

 work which has led to its commercial 

 production in the United States. 



Egyptian cotton differs from any 

 other commercially grown cotton, al- 

 though showing many points of simi- 

 larity to the American Sea Island. The 

 parentage of this type, which originated 

 in Egypt about seventy-five years ago, 

 is" obscure. Some authorities believe it 

 to have resulted from hybridization of 

 Sea Island with a brown linted African 

 tree cotton, both of which were grown 

 in -Egypt during the early part of the 

 nineteenth century. ^ However this may 

 be, the type is now a well-defined one, 

 and while it comprises several distinct 

 varieties, all of these share certain 

 peculiarities which distinguish them 

 from other commonly cultivated cottons. 



Commercially, Egyptian cotton is 

 characterized by the superior strength 

 and by the color of the fiber, the latter 

 \'arving from light brown^ in some 

 varieties to pale buff or nearly pure 

 white in others. 



'' The length of the fiber ranges, in the 

 different varieties, from P/ie to 1% 



1 See Balls, W. L. The Cotton Plant in Egypt. London, 1912. The origin of the Egyptian 

 type is discussed on pages 3 and 4. 



"^ Balbriggan underwear was formerly manufactured only from the undyed fiber of brown 

 Egyptian cotton. 



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