423] 8. F. T release 225 



Perhaps the main result of this study is, in general, that 

 no matter whether we employ (1) the three salts KH 2 P0 4 , 

 Ca(X0 3 ) 2 , and MgS0 4 , (2) the four salts KH 2 P0 4 , 

 Ca(X0 3 ) 2 , MgS0 4 , and KX0 3 , or (3) the four-salts KH 2 P0 4 , 

 Ca('N0 3 ) 2 , MgS0 4 , and KC1, if we use the best proportion* 

 of the salts in each case we may expect to obtain about the 

 same growth. This generalization has an important bearing 

 on the whole problem of physiological balance in nutrient 

 solutions and furnishes what may be important suggestions 

 bearing on our general conceptions of conditional control and 

 conditional optima for plant activities. 



THE RELATION OF THE CONCENTRATION OF THE 



NUTRIENT SOLUTION TO THE GROWTH OF YOUNG 



WHEAT PLANTS IN WATER-CULTURES 



By S. F. TRELEASE 



In these experiments the salt proportions were the same in 

 all the different solutions of each series, but the solutions 

 differed from each other in total concentration. Three series 

 of cultures, all carried out at the same time, are considered, 

 each series including a concentration range of from 0.5 to 7.0 

 atmospheres. A different set of salt proportions was used in 

 each series. Six plants were grown in each culture and the 

 cultures were in duplicate, upon a rotating table. The ex- 

 periment lasted for 32 days, from January 23 to February 

 24, 1917, the solutions being renewed every 4 days. 



In the first series the nutrient solutions contained the 4 

 salts KH 2 P0 4 , MgS0 4 , KC1, and Ca(X0 3 ) 2 in the follow- 

 ing relative molecular proportions: 1.000, 0.587, 0.485, 0.341. 

 The average dry weight of tops and the average total water 

 loss by transpiration, for six plants, are shown in the follow- 

 ing table, whch also shows the total concentration employed 

 in all three series. 



