17, 6 Trelease: Salt Requirements of Wheat Plants 571 
est and lowest top and highest and lowest root water require- 
ments, though there was general agreement between the high 
and low and medium areas for the two series. The general 
features are the same as those for the preceding series and will 
not be discussed in detail here. 
SERIES III 
METHODS OF SERIES III 
Series III extended over thirty-two days, from December 4, 
1916, to January 5, 1917. The maximum temperature for this 
period was 28° C. (December 8, 13, 14, 21), and the min- 
imum was 12° C. (December 15, 17, 30). The average daily 
maximum for the period was 25° C., .and the average daily 
minimum was 16°C. The mean daily water loss from the at- 
mometer was 15.7 cubic centimeters, and the total loss for the 
period was 501 cubic centimeters. 
All of the culture solutions employed in this series had the 
Same total concentration (1.60 atmospheres) as was used in 
series I and IJ. But much higher partial concentrations of 
potassium chloride were included in this series, since the results 
obtained from the preceding series showed no very pronounced 
effects that might be attributed to potassium chloride. Four 
sets of culture solutions were used, in which potassium chloride 
contributed 0.2, 0.7, 0.8, and 0.9, respectively, of the total os- 
motic concentration. In each of these sets ten combinations of 
the other three salts were tested. The method of varying the 
other three salts may be most easily understood by referring to 
the diagrams of fig. 7. Each of the four triangles (T2, T7, T8, 
T9) represents one of these four sets. The cultures of the 
first set (T2) have 0.2, those of the second (T7) have 0.7, those 
of the third (T8) have 0.8, and those of the fourth (T9) have 0.9 
of their total osmotic concentration due to potassium chloride. 
In each of the sets the residual osmotic concentration is dis- 
tributed among the other three salts in the way shown by the 
distribution of the dots on the diagrams. Thus in triangle 2 
the distribution was 0.8 of the total concentration; in triangle 7, 
0.3; in triangle 8, 0.2; and in triangle 9, 0.1. Each of the cul- 
tures indicated on the triangular diagrams of fig. 7 represents 
various proportions of monopotassium phosphate, calcium ni- 
trate, and magnesium sulphate, the amount of potassium chloride 
being indicated by the number of the triangle. Thus the cul- 
