16, 5 Espino: Salt Requirements of Young Rice Plants 495 
not at all understood and partly because the possible errors in cut- 
ting, weighing, etc., are much greater for roots than for tops, the 
same general plan will here be followed as was resorted to in 
the case of the top yields. Attention will be mainly restricted 
to the two medium total concentrations, series 15 and 19. 
Before leaving the general] subject of total concentration it 
may be remarked that the low and the high root yields are not 
in any case as clearly segregated as are the corresponding ones 
for tops; but, with the higher total concentrations, there is a 
marked tendency for low values to correspond especially to the 
third, fourth, and fifth triangles of the tetrahedral diagram; 
that is, to high relative partial concentrations of monopotassium 
phosphate. As in the case of top yields, the most certainly well- 
balanced sets of salt proportions have low relative partial con- 
centrations of this salt, 
In connection with Table 7 it has been noted that the limited 
_ information at hand appears to indicate that the lower of the 
_two medium total concentrations may be appreciably better for 
root yields, as well as for top yields, than is the higher. Since the 
differences are not great, they require no emphasis at this time, 
however. 
The agreements and disagreements between the similar se- 
ries, With regard to root yields, are given in Table 8, the notation 
of which has already been explained. Reference to that table 
brings out the fact that the following five sets of salt proportions 
agreed in giving high root yields for all five trials: T1R1S1, 
T1R1S2, T1R1S3, T1R2S1, and T2R1S1. The first two and the 
fourth one of these have been noted as showing the same out- 
standing agreement for top yields. None of the solutions show 
this kind of agreement for low root yields. 
TOP AND ROOT YIELDS IN RELATION TO SALT PROPORTIONS 
The relations between yield and salt proportions may be 
brought out best by the use of the tetrahedral diagram. The 
symbols shown in Table 8, for tops and for roots, and for the 
low-medium and high-medium total concentrations, are plotted 
diagramatically in figs. 4 to 7. The only alteration made in 
entering the letters on the diagrams has been to change HL to 
M, on the supposition that a solution giving high yield in one 
trial and low yield in another trial should be represented as 
belonging to the medium group. The areas of the diagrams 
representing high yields and those representing low yields are 
distinguished by shading. In outlining these areas, combinations 
