^6 THE AMERICAN BOTANIST 



For some months I have been in correspondence with a 

 considerable number of Agricultural Experiment Stations on 

 the question of producing disease resistant plants, and here I 

 will refer to some of the experiments at two of these as being 

 illustrative of points which I wish to call to the attention of 

 readers. 



At Pullman, Washington, Dr. E. F. Gaines has been ex- 

 perimenting on the production of disease resistance in a vari- 

 ety of plants. Referring to a variety of wheat he says that 

 "selection within a pure line under conditions favoring maxi- 

 mum infection has not changed the resistance of a given vari- 

 ety during five generations." Speaking of another variety 

 originating in a cross he says that "the immune selections 

 have not changed in genetic characteristics during the seven 

 generations that they have been grown in the smut nursery." 

 Here we see that when other conditions remain constant, 

 selection accomplishes nothing in the w-ay of increasing the 

 disease resistance of the plants being experimented upon. 



At the Agricultural Experiment Station at Agricultural 

 College, North Dakota, Professor H. L. Bolley planted one 

 seed from a non-resisting variety of flax on soil which was 

 slightly infected with wilt disease, but not infected enough to 

 kill the plant. From the plant thus grown on slightly sick 

 soil he took one seed which he planted on soil slightly more 

 infected than the year previously. From this second plant he 

 took one seed and planted it the third year on soil still more 

 infected. And so on. 



In regard to this process. Prof. Bolley says that he has 

 "never been able to procure a fvill-fledged wilt-resisting plant 

 from the first generation," but that after six or seven years 

 of this procedure he has flax plants which will thrive on soil 

 so heavily infected that the original stock "could not produce 



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