1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 35 
T X 
(Series 4, III—Peas [dry, high temperature]) 
SALT REQUIREMENTS AND H-ION CONCENTRATION IN RELATION TO GROWTH 
Total | Gr. wt. | Total | Greatest Pa 
No. Pa gr. wt. | of roots | dry wt. | length 
indices | (gms.) | (gms.) | (gms. | (cm.) | Initial | After gr. 
1 | ApO 7.42 | 3.05 952 | 23.68 | 3.4 4.6 
2 | Ap/5 10.62 | 3.55 | 1.026 | 24.63 | 4.6 5.0 
3 | Ap/10 13.95 | 4.49 | 1.101 | 27.63 | 5.8 5.4 
4 | Apl/ 3.20 | 1.10 642 | 11.82 | 3.35 5.3 
5 | Ap3/ 6.78 | 2.47 796 | 18.84 | 3.15 5.0 
6 | ApNa 11.22 | 3.60 945 | 25.33 | 3.45 4.4 
7 | ApM 10.00 | 3.89 | 1.095 | 23.57 | 5.4 5.6 
8 | BpO 12.79 | 4.37 | 1.023| 24.06 | 6.6 4.5 
9 p /5 12.97 | 4.15 | 1.059| 25.96 | 7.4 7.3 
10 | Bp/10 12.90 | 4.12 | 1.027| 26.05 | 8.6 7.4 
11 | Bp1/ 8.64 | 2.15 877 | 2111 | 6.4 7.0 
12 | Bp5/ 11.95 | 4.27 948 | 2423 | 3.2 6.1 
13 | Bp10/ 2.97 | 0.75 432 9.95 | 2.8 3.0 
14 | BpK,/10 | 14.32| 4.90 | 1.130 | 27.37 | 7.0 7.3 
15 | BpCa 14.44 | 4.92 | 1.223 | 26.33 | 7.3 7.8 
16 | C 6.60 | 2.10 929| 16.91 | 4.2 6.0 
17 | Cp/5 11.65 | 3.50 | 1.046 | 2143 | 6.4 6.6 
18 | Cp/20 5.11 | 1.22 760 | 15.40 | 7.6 7.6 
19 | Cp1/ 10.97 | 3.45 977 | 21.28 | 3.6 5.4 
20 | Cp5/ 5.40 | 1.25 .636 | 15.54 | 3.2 5.8 
21 | CpNa 8.75 | 2.45 .966 | 18.99 | 4.2 6.0 
hydrogen ion concentration is marked. In general, as the con- 
ditions of evaporation are intensified it would appear that some- 
what more favorable results are obtained with this plant when . 
the hydrogen ion concentration does not approach too closely 
the acid limit. 
It is clear, however, that the preparation of nutrient solutions 
with acid phosphate—even though of high grade—may mean, 
and often does mean, a hydrogen ion concentration either peril- 
ously near the critical region for growth, or actually inhibiting 
growth. This is particularly true for wheat, and it may be true 
for corn and other crops under any conditions which may accen- 
tuate acid injury. Pronounced diminution in growth may occur 
as the Py exponent is progressively diminished from about 4.5. 
For each plant in the preceding series a separate set of curves 
(figs. 5, 6, and 7) has been prepared; and in each figure there are 
