i7, 6 Trelease : Salt Requirements of Wheat Plants 569 
yields of tops were restricted to cultures having values of the 
Mg/Ca-ratio ranging from 0.53 to 3.52 for series I, and from 0.53 
to 1.73 for series II, while the total range for each of these entire 
series was from 0.21 to 13.43. Thus high yields of tops were 
never obtained when the Mg/Ca-ratio value was above 3.52, no 
matter what the proportions of the other ions. High yields of 
tops were obtained when the Mg/K-ratio had the lowest value 
tested (0.14), and were restricted to relatively low values of 
this ratio. The highest value of the Mg/K-ratio that gave high 
yields was 0.93, while the highest value tested was 4.64. High 
yields of tops were also restricted to low values of the Ca/K- 
ratio, never being obtained when this was higher than 0.73, 
while the highest value for the entire series was 2.68. The very 
lowest value (0.08) of the Ca/K-ratio also produced high yields 
of tops. The data presented in this table may be summarized by 
stating that low yields were obtained with practically all ratio 
values tested ; but that high yields were never obtained when the 
Mg/Ca-ratio was higher than 3.52, nor when the Mg/K-value 
was above 0.93, nor when the Ca/K-value was above 0.73. 
Culture T1R1C1, which gave the lowest yields of tops in se- 
ries I and II, had the following ratio values: Mg/Ca, 13.43; 
Mg/K, 4.68; Ca/K, 0.35. The other culture in series II giving 
a yield as low as T1R1C1 (namely culture T2R1C1) had the fol- 
lowing values: Mg/Ca, 11.35 ; Mg/K, 2.61 ; and Ca/K, 0.23. The 
highest yields of tops were obtained, in series I, with culture 
T2R4C2 having the following ratio values: Mg/Ca, 1.72; Mg/K, 
0.40; Ca/K, 0.23; and in series II, with culture T2R4|C1| having 
the ratio values: Mg/Ca, 1.72; Mg/K, 0.29; Ca/K, 0.17. These 
two solutions are characterized by equal Mg/Ca-ratios ; but the 
other two ratios are different for the two solutions. 
The relations between cation-ratio values and root yields for 
series I and II are shown in Table 10. Considering the results 
of the two series together, it is apparent that there is little or no 
relation between low root yield and the value of any one of the 
three cation ratios. This agrees with what was found for top 
yields. However, as in the case of top yields, there was an 
apparent relation between high yields and cation-ratio values. 
Thus, high root yields were obtained only when the Mg/Ca-ratio 
had values from 0.21 to 5.48, while the total range for the 
series was from 0.21 to 13.43. In a similar way high root 
yields were restricted to low values of the Mg/K-ratio, from 0.14 
to 0.80, and never occurred with ratio values between 0.80 and 
4.68. On the other hand, there was no relation between high 
