226 Concentration of Nutrient Solutions [424 
Concentration, Dry Weight, Tops, Transpiration, 
atm. grams, ce. 
0.5 0.926 651 
1.0 0.947 618 
1.6 1.152 646 
2.5 1.117 554 
3.5 1.030 468 
4.5 0.904 386 
5.5 9.821 311 
7.0 0.769 246 
For this particular set of salt proportions the maximum 
yield of tops was obtained when the nutrient solution had a 
total osmotic concentration of 1.6 atm. With lower con- 
centrations growth was considerably less, as is also true, and 
to a greater degree, with concentrations above the optimum. 
Between the concentrations 1.6 and 7.0 atm. the dry weight 
ef tops is approximately a linear function of the concentra- 
tion, the dry weight decreasing as the concentration icreases. 
The transpiration values show the same general relation to 
the concentration, except that below 1.6 atm. the -decrease is 
less clearly shown; in fact, with a concentration of 0.5 atm. 
the transpiration is slightly higher than with 1.6 atm. 
In the second series the culture solutions were the same 
as those just described, except that KCl was not included. 
Jn these cultures the relations of dry weight and transpira- 
tion, to total concentration, were essentially the same as in 
the cultures of the first series, with Cl. 
In the third series the salts used were the same as in the 
first, but in different relative molecular proportions, as fol- 
lows: 1.000, 1.155, 7.282, 0.699. The relation between trans- 
piration and concentration was the same as in the first series, 
but in this case there was a perfectly definite maximum of 
transpiration at 1.6 atm. For production of dry weight of 
tops, however, while the general relation to concentration was 
the same as in the first two series, the optimum concentra- . 
tion was 4.5 instead of 1.6 atm. 
The interesting features of these results may be summar- 
ized as follows: (1) Transpiration and dry weight showed 
an approximately linear relation to the concentration of the 
medium above the optimum, these decreasing with an increase 
in concentration. (2) The optimum concentration for dry 
