421] S. F. Trelease 223 
employed by Tottingham and by Shive.t 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. Highty-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 KCl, 0.0138M 
KH,PO,, 0.0047M Ca(NO,),, and 0.0081M MgSO, 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 
*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. |: 327-397. 1915. 
