16, 5 Espino: Salt Requirements of Young Rice Plants A471 
tures. Lack of time prevented the actual determinations of the 
freezing points of the solutions used in these experiments. 
The three series of stock culture solutions will now be de- 
scribed in order. 
Three-salt type I.—Fifteen different sets of molecular salt 
proportions were tested for this solution type. The fifteen dif- 
ferent stock culture solutions all agree in having a total of 
0.0245 gram-molecule of salt per liter and the molecular partial 
concentration of each of the three salts differs from solution 
to solution throughout the series by increments of one-seventh 
of the total molecular concentration; that is, by increments of 
0.0035 gram-molecule. These fifteen different 3-salt stock so- 
lutions may be designated according to the positions of the points 
representing them on a 3-coérdinate diagram similar to the one 
used by Schreiner and Skinner, Shive, and others. The diagram 
here used is shown in fig. 1. The different sets of molecular 
salt proportions will be named by formulas similar to those 
employed by Shive, only that the 
letter S will be here used (for 
solution) instead of C (for cul- 
ture). R1S1 is the solution rep- 
resented by the lower left apex 
of the triangular diagram; R1S3 
is the one represented by the third 
point from the left end of the 
lowest row of points; R3S3 is rep- 
resented by the third point, count- 
ing from the left, in the third row; ° 
R581 is represented by the top 
meen Of thé. diagram ‘(sitce the ") Soe er ea cost Ga 
fifth row has but a single point) e crements of one-seventh, tc#al concen- 
etc. In this diagram every so- cca righ peaee. crerar mag ere 
lution of the lowest row has one- shaded area includes ae Sapaeoe sets 
Seventh © of ite total molecular SO. SS 
concentration made up of monopo- 
tassium phosphate, every one on the left margin has one-seventh 
made up of calcium nitrate, and every one on the right margin 
has one-seventh made up of magnesium sulphate. 
The different sets of molecular salt proportions and the mo- 
lecular partial concentrations of the one salt monopotassium 
Phosphate are shown in Table 1. From these data the molec- 
ular partial concentrations of the other two salts can be readily 
computed. 
171114——3 
