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THE AMERICAN NATURALIST [Vol. XLIII 



the uniformity of vegetative strains upon vegetative propagation. 

 As soon as individual wheat plaids are crossed, even inside the 

 same variety, a wide range of diversity reappears. Self-fertiliza- 

 tion, like vegetative propagation, brings uniformity by suppres- 



mitted. and at once reappear when hybrids are made, or selection 

 is relaxed, or the plants are transferred to new conditions. 



It is true that uniformity like that of the pure strains of 

 domesticated varieties is sometimes found in nature, but even 

 this does not prove that uniformity represents a truly normal 

 condition of reproduction. Having learned that artificially 

 restricted descent produces uniformity in domesticated varieties, 

 it is easy to understand that natural conditions of close breeding 

 can also produce uniformity. 



The methods of reproduction that yield uniform offspring 

 often appear very effective from the environmental standpoint, 

 but this only shows the more plainly their physiological in- 

 feriority. All indications point to the probability that long- 

 continued vegetative propagation, self-fertilization or close 

 breeding bring the same deterioration, sterility and ultimate 

 extinction to wild types as to domesticated varieties. It does 

 not appear that the vigor and fertility of organisms can be 

 permanently maintained by the methods of reproduction re- 



el i an inheritance a definite evidence of the abnor- 

 ations, but the significance of this relation is not 

 ted until we perceive that the uniformity of pure 

 y marks a first step toward degeneration. 

 D. C, 

 10. 1909. 



O. F. Cook. 



