July 15, 1914 
Mutation in Egyptian Cotton 
299 
influence of hybridization is the disturbance of germinal equilibrium 
which manifests itself in the production of mutants. Since, furthermore, 
the distinctive characters of the mutants were not observed, singly or in 
combination, among nearly related individuals of the parent stock, the 
"germinal instability” theory of Gates appears preferable to the "Men- 
delian recombination” hypothesis of Heribert-Nilsson as an explanation 
of the known facts regarding mutation in Egyptian cotton. 
Whatever may be the true explanation of the mutability of Egyptian 
cotton, there can be no question that the occurrence of mutants of a 
desirable character, and the relative uniformity during several genera¬ 
tions of the resulting varieties, have been a safeguard to the cotton 
industry of Egypt. As fast as the old varieties have deteriorated through 
crossing with one another and with Hindi cotton, new varieties have been 
at hand to replace them. 
In the varieties which have developed in Arizona, persistent roguing 
has so nearly eliminated the Hindi and Upland elements that they are 
scarcely detectable upon careful examination of thousands of plants 
(see p.292). These varieties may therefore be expected to remain uniform 
much longer than those which are grown in Egypt, provided that they are 
kept isolated from each other and from other types of cotton. If, not¬ 
withstanding, deterioration should ultimately take place, the mutability 
of the type affords ground for the hope that new varieties of equal or 
greater value will be forthcoming. The contingency should, however, 
be borne in mind that these varieties, so long as they are protected from 
crossing with other forms, are likely to be less productive of mutants 
than was the heterogeneous stock of the Mit Afifi variety from which they 
originated. 1 It is significant in this connection that in the Yuma variety 
during seven generations only one striking and desirable mutant has been 
detected among thousands of plants and that in the Pima variety, which 
is derived from the mutant in question, no tendency to further mutation 
has yet been observed. 
SUMMARY 
The origin of the Egyptian type of cotton is obscure. According to 
one theory, it is a product of hybridization between a brown-linted tree 
cotton and American Sea Island, both of these types having been culti¬ 
vated in Egypt nearly a century ago. Whether or not this be true, there 
can be no question that the varieties now grown are of mixed ancestry, 
a condition which some investigators regard as favorable to mutation. 
Numerous varieties have appeared from time to time in Egypt. The 
Ashmuni variety, now grown only in Upper Egypt, originated about 1850, 
This variety gave rise in 1887 to the Mit Afifi, and from the latter the 
1 " As a rule the new species proved much less mutable than the original O. Lamarckiana from which they 
originated. It is only the inconstant forms amongst them which exhibit a very high degree of mutability, 
as, for example, O. scinttllans .** (De Vries, 1909, v. 1, p. 296.) 
