i7, 6 Trelease: Salt Requirements of Wheat Plants 583 
largest amounts of calcium nitrate and the smallest amounts of 
magnesium sulphate; that is, by low Mg/Ca values. These 
results indicate, therefore, that an increased proportion of potas- 
sium chloride gives increased root production, except in solu- 
tions having very low Mg/Ca values. 
SERIES IV 
METHODS OF SERIES IV 
Series IV lasted thirty-two days, from January 23 to Feb- 
ruary 24, 1917, the period being of the same length as for series 
III. The maximum temperature during this period was 29° 
C. (February 4, 17, 21) and the minimum was 7° C. (February 
11). The average daily maximum for the period was 25° 
C. and the average daily minimum was 13° C. The mean 
daily evaporation rate from the atmometers was 15.3 cubic 
centimeters, and the total loss was 491 cubic centimeters. 
In this series it was planned to study the effect upon the 
plants of different total concentrations for the same set of salt 
proportion's. Only three of the eighty-four sets were tested in 
this way, and with them was tested a three-salt solution, 
without potassium chloride, having the salt proportions nearly 
the same as those in Shive’s best solution for wheat. For each 
one of these four sets of salt proportions eight different total 
concentrations were employed. The three sets of four-salt pro- 
portion's used were as follows: (1) T7R1C1, which contained 
the maximum amount of potassium chloride occurring in any 
of the eighty-four solutions; (2) T1R1C1, which contained the 
maximum amount of magnesium sulphate present in any of the 
eighty-four solutions and which also had the poorest physio- 
logical balance for dry top yield in these plants; (3) T2R4C2, 
which had the best physiological balance for dry top yield. The 
three-salt solution in this series was one that is to be designated 
as R5C2^ on the Shive diagram. 
For each one of these four sets of salt proportions the eight 
total concentrations tested, expressed in terms of their osmotic 
values, were as follows: 0.50, 1.00, 1.60, 2.50, 3.50, 4.50, 5.50 
and 7.00 atmospheres. It will be noticed that the third one of 
these concentrations (1.60 atmospheres) is the one employed in 
all of the preceding series. 
The calculations were based upon the data given for series 
I, and the various concentrations were obtained by first prepar- 
ing a solution having an assumed osmotic value of 7.00 atmos- 
