421] 8. F. Trelease 223 



employed by Tottingham and by Shive. 4 The total concen- 

 tration of the nutrient solution corresponded to an osmotic 

 pressure of approximately 1.6 atmospheres at 25 C., and the 

 relative proportions of the four component salts were varied 

 in all possible ways, by increments of one-tenth of this total 

 concentration. Eighty-four different solutions were thus in- 

 cluded in each complete set; all of these had approximately 

 the same total osmotic concentration, but no two had the 

 same relative proportions of the four component salts. Six 

 plants were grown in each culture, and the solutions were 

 renewed every four days. 



The various salt proportions proved to be very different in 

 their ability to produce growth of the young wheat plants. 

 As has been found by other writers, the solution giving the 

 greatest dry yield of tops is not the one giving the greatest 

 yield of roots, and the solution producing the highest dry 

 weight of tops and roots together has still another set of salt 

 proportions. The highest dry yield of tops was obtained 

 with the following partial volume-molecular concentrations 

 of the four main constituent salts: 0.0067M KC1, 0.0138M 

 KH 2 P0 4 , 0.0047M Ca(N0 3 ) 2 , and 0.0081M MgS0 4 . A 

 trace of iron was, of course, added, as a suspension of ferric 

 phosphate. 



This highest yield of wheat tops with the 4-salt solution 

 containing chlorine was not higher, however, than was ob- 

 tained, in these experiments, with the best salt proportions, 

 without chlorine, of the Birner and Lucanus (Shive) 3-salt 

 solution and of the Knop (Tottingham) 4-salt solution. If 

 the best salt proportions are used in all three cases these three 

 very different types of solutions give practically the same 

 result. It therefore appears to be impossible to improve the 

 growth of young wheat plants, as this occurs in Shive's and 

 Tottingham's best salt proportions, by the introduction of 



4 Shive, J. W., "A three-salt nutrient solution for plants." Amer. 

 Jour. Bot. 2: 157-160. 1915. Idem, "A study of physiological bal- 

 ance in nutrient media." Physiol. Res. I: 327-397. 1915. 



