444 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
12. Conclusion: The increased ratio of tops to roots which results from 
increasing the amount of nitrate in the solution may be explained on the 
basis of increased use of carbohydrates in the tops because the greater 
nitrogen supply makes for greater growth. This results in a decrease in 
the supply of carbohydrates for the roots, which may bring about an 
absolute or a relative reduction of root growth. 
This study was carried out in the laboratory of plant physiology at 
Cornell University, and the writer is deeply indebted to Professor O. F. 
Curtis, who suggested the problem, for valuable and helpful criticisms in 
the course of the work. The writer also owes thanks to Professor H. H. 
Love of the plant-breeding department, who furnished the pure line of 
barley used, and to Professor C. H. Hutchinson of the same department for 
the pure line flax seeds. 
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