1920] WA LSTER—BA RLE Y r 2 5 



and a high nitrogen supply at an early stage in the development of 

 the barley plant so shifts the equilibrium toward excessive vege- 

 tation as to prevent the normal tendency toward reproduction. 

 Some other factor must be altered, therefore, as, for example, the 

 water supply, if such plants are to be thrown into reproduction. 



An investigation of the nitrogen-carbohydrate ratio at a differ- 

 ent stage in the development of seeds and seedlings furnished with 

 varying concentrations of nitrogenous compounds will probably 

 throw considerable light upon these questions. 



Conclusions 



1. The excessive leaf production in the high temperature barley 

 is caused by the high concentration of nitrates in the nutrient 

 supplied. 



2. Nitrate nitrogen in the nutrient begins to affect the subse- 

 quent course of development at high temperatures at the time of 

 germination, or at least at a very early stage in the development of 

 the plant. The tendency to excessive vegetation thus inaugurated 

 cannot be counteracted by the addition of phosphorus or potassium 

 salts. 



3. The effect of the nutrient supply is reflected in the compo- 

 sition of the active organ, the leaf. The following equations rep- 

 resent the main facts revealed by chemical analysis of the leaf : 



High heat supply +high nitrogen supply in nutrient solution = 

 high soluble nitrogen in leaf + low soluble carbohydrate = excessive 

 vegetation and little culm formation. 



Low heat supply + high nitrogen supply in nutrient solution = 

 low soluble nitrogen in leaf + high soluble carbohydrate = normal 

 vegetation and normal culm formation. 



The writer gratefully acknowledges his indebtedness to Professor 

 William Crocker for helpful advice and criticisms; to Professor 

 F. C. Koch for valuable advice and laboratory facilities; and to 

 the Department of Zoology of the University of Chicago for facilities 

 afforded in their greenhouses. 



AGRICULTURAL COLLEGE 



N.D. 



