No. 495] 



CONSTANCY OF MUTANTS 



179 



be active in nature even though mutations are observed. 

 Or, perhaps plainer, it is equivalent to saying that muta- 

 tions themselves may be nothing more or less than adap- 

 tations, adaptive changes. I think breeders who ignore 

 this thought in their work will eventually find themselves 

 without a basis for well-founded experiments. 



I have been brought to these conclusions chiefly through 

 careful observations upon my own selection and breeding 

 plots, upon which for a number of years, I have attempted 

 to hasten the survival of the fittest, or of the unlike, 

 through the development of or heightening of the action 

 of plant disease for the purpose of eliminating the weak 

 or unfit. 11 The method of field work consists essentially 

 in constant culture or cropping to the crop under con- 

 sideration and in promoting, in every way possible, the 

 development and action of the disease under considera- 

 tion; and at the same time using all available methods 

 of breeding and selection under these heightened condi- 

 tions of disease. The method has given marked results 

 when applied to wheat vs. wheat rust; wheat vs. wheat 

 smut; flax vs. flax rusts; flax vs. flax wilt; and potatoes 

 vs. scab and blight. 



My observations along these lines have been such that 

 I have no fear but that the future will find me right in 

 the assertion (1) that mutants may be so insignificant 

 and numerous as to be unrecognizable and thus fall di- 

 rectly into the class called by DeVries, "fluctuating vari- 

 ations"; or (2) that they may be induced in a mixture 

 of a great number of varieties of a species at one and the 

 same time because of the same environmental causes ; or 

 (3) that, in some cases, " fluctuating variations" are of 

 such nature and worth as to allow results to be obtained 



Station and in an address delivered 1 

 stockmen at St. Louis, October, 1903, 

 I, page 131 of the report of this assoc 

 of the Lansing Meeting of the Socie 



