1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 11 
peas 18. The solutions were renewed and water loss was sup- 
plied as previously noted. The determination of the hydrogen 
ion concentration “after” growth in the case of corn furnishes 
an index of the change in the solution after the plants had grown 
in it for 10 to 12 days, representing the final interval. In this 
particular case the intervals between changes of solution were 
made rather long, with the idea of emphasizing conditions. The 
experiments were begun early in November under favorable 
growing conditions. The daily evaporation rate from a stan- 
dardized spherical evaporimeter averaged 11 cc. per day. 
TABLEI 
(Series 1, Wheat) 
SALT REQUIREMENTS AND H-ION CONCENTRATION IN RELATION TO GROWTH; 
SOLUTIONS A AND B 
Total Total Greatest +7 
No. Culture gr. wt. dry wt. length Initial Pa 
indices (gms.) (gms.) (cm.) of sol. 
1 AwO 4.92 0.4077 24.32 4.0 
2 Aw /5 4.62 0.3916 23.89 5.6 
3 Aw /10 5.20 0.4135 23.69 5.9 
4 Aw /15 3.94 0.3550 21.24 6.1 
5 AwNa 4.72 0.3792 25.93 4.0 
6 BwO 4.52 0.3545 24.19 7.0 
ri Bw /5 4.94 0.3498 23.36 8.4 
8 Bw /10 5.83 0.4090 22.27 9.0(+) 
9 Bw 5/ 2.53 0.2522 16.48 4.6 
10 Bw 10/ 0.69 0.1176 8.26 3.2 
11 Bw 20/ 0.67 0.1134 6.56 3.0(—) 
12 BwK;/10 6.38 0.4390 26.34 6.2 
13 BwK;/20 5.80 0.3996 25.94 6.2 
From series r, table r, also fig. 1, it is seen that with wheat 
there is indication that the addition of a certain amount of 
alkali, shifting slightly the H-ion concentration, is beneficial, 
though Aw/5 is irregular. Wholly unexpected is the extent of 
the growth in certain of the B cultures. Introduced empirically, 
this solution has not only yielded well, but in their vigorous, 
green appearance these cultures rank highest. The addition of 
alkali to solution B is beneficial, possibly from the addition of 
the sodium ion or from the slight increase in the concentration 
