1922] JONES & SHIVE—WHEAT SEEDLINGS 397 
enced by the growing wheat plants than did the solution of BIRNER 
and Lucanus. These comparisons, of course, are made upon the 
assumption that the plants in all the cultures were approximately 
equal with respect to their ability to cause reaction change. 
The Py values recorded in table IV were determined in the 
same manner and at the same intervals during the same time 
period as were those given in table III. The initial H ion con- 
centrations of the LivincsTton-ToTTINGHAM (9) solutions contain- 
ing dihydrogen potassium phosphate are always much lower than 
TABLE IV 
Px VALUES OF NUTRIENT SOLUTIONS DETERMINED AT INTERVALS DURING CONTACT 
WITH ROOTS OF GROWING WHEAT PLANTS 
P,, VALUES 
Duration of intervals in hours 
InI- 
TYPE NUMBER TIAL 
2 4 | 6 B.5 01 84:5: 1 97 1 30.6) 38 52 
Livingston-Tottingham three-salt solutions 
I Matec... 4 4:9 (a8) 6.6 1 6:41 5.416.415.5156 15.9 
II Ba es. 9.814.817 6.674e 1 6.2) 44 1 O81 550 1 5-3 1-8-8 
Ill | Ae ae 5.6 1 3:.6:14.57 4% 614.61 4.514:3 | 4.6.1 4.8 1.5.6 
y. itn Ma 9 aS P46 140A 4S 1 4-3 1 425 1 4-7 | 5.6 
a RB 66 3.6 | 3.6 | 3.7 | 3.8 | 3.90 | 4-3 | 4-3 | 4:3 | 4.4] 5-4 
VI Me ieee, 4:3 14:7 | &7 F400 | S10 | 8:21 5.4153 | §-41.5-6 
Modified Tottingham solutions 
TR Ae. os 4849 9|5-.0| 5.0] 4.7| 4.6 | 4.6 | 4.6] 4.2 
Teg as 4:8 (4.014.601 $:0 14-0 54-61 6.4) 6-4) 6-4 [4:2 
are those containing the corresponding calcium or magnesium 
salts. This fact is more certainly brought out by McCatr and 
Haac’s (10) table of Py values determined for six complete series 
of the Livincston-TorrincHAM type-solutions described in a 
publication (8) prepared for a special committee of the Division of 
Biology and Agriculture of the National Research Council. 
Mention should be made of the fact that the initial Py values 
of the solutions here chosen as representatives of types III, IV, V, 
and VI, as given in table IV, are not in very close agreement with 
those determined for the same solutions by McCatr and Haac. 
