16,6 Trelease: The Growth of Rice 613 
might be expected. With this exception, all the cultures having 
high proportions of ammonium sulphate gave high yields of 
tops. An examination of this diagram with reference to the 
proportions of the other two salts shows that high yields of tops 
were not obtained when potassium sulphate made up more than 
0.4 of the total osmotic value of the mixture, but that many cul- 
tures having low proportions of this salt gave only medium or 
low yields. Furthermore, it is seen that high yields were not 
obtained when primary calcium phosphate comprised more than 
0.5 of the total osmotic value, but that low or medium yields 
were obtained in many cultures in which this salt made up only 
a small proportion of the complete salt mixture. It is evident 
that high yields were definitely correlated with high proportions 
of ammonium sulphate (supplying the element nitrogen to the 
plants), and that high yields were not obtained with the highest 
proportions of potassium sulphate and primary calcium phos- 
phate, but could not be related definitely to low proportions of 
these two salts. 
It will be noted that the highest yield of tops was obtained 
with culture R1C8, having the following fertilizer mixture: 
0.0154 gram molecule of primary calcium phosphate, 0.1228 
gram molecule of amonium sulphate, and 0.0154 gram molecule 
of potassium sulphate. This salt mixture contains the highest 
proportion of ammonium sulphate tested, and the lowest propor- 
tions of primary calcium phosphate and potassium sulphate. 
The great increase in growth resulting from the addition of 
the fertilizer is shown by the fact that the yield of tops with 
the control culture, which was without fertilizer, was only 19 
per cent of that obtained with culture R1C8. 
Turning now to areas of low yields, it will be observed that 
these include a single row of cultures at the extreme left-hand 
margin of the triangle, together with two other cultures: R2C2, 
close to the left-hand margin; and R6C3, in the upper part of 
the right-hand margin. The latter culture, R6C3, is apparently 
abnormally low, occupying a region generally characterized by 
medium yields. Aside from this apparently exceptional cul- 
ture, low yields are confined to cultures having very small 
amounts of ammonium sulphate; all of the cultures giving low 
top yields except R2C2 and R6C3, had only 0.1 of the total 
osmotic value of their salt mixtures due to ammonium sulphate. 
Inspection of the diagram with reference to the proportions 
of the other two salts—potassium sulphate and primary calcium 
phosphate—shows that low yields were obtained with all the 
