proportions possible for each solution type, just twenty-one; 

 and we select them so as to be representative of the mathematic- 

 ally possible range of sets of proportions. This is accomplished 

 by letting the volume-molecular partial concentration of each 

 salt differ from solution to solution (in a series of twenty-one 

 solutions, all with the same total concentration, measured osmot- 

 ically) by increments of one-eighth of the total volume-molecu- 

 lar concentration. Previous workers in this field have mainly 

 used increments of one-tenth, and have employed osmotic pro- 

 portions instead of volume-molecular proportions. For each of 

 the six types of solution (numbered in Roman numerals above) 

 all the possible sets of salt proportions, with increments of one- 

 eighth, are represented by the points in a triangular diagram, 

 as first used in this sort of work by Schreiner and Skinner (U. 

 S. Bur. Soils, Bull. 70, 1910. Also Bot. Gaz. 50: 1-30. 1910.) 

 and later by Shive, McCall, Hibbard. (See Shive — 1915 — for 

 the general plan of such a diagram, but it is to be remembered 

 that he used increments of one-tenth and thirty-six sets of pro- 

 portions, while we employ increments of one-eighth and have 

 only twenty-one sets.) In diagraming the solutions for the 

 present project it is earnestly requested that all diagrams follow 

 the same system. Let the base line for the potassium salt be the 

 base of the triangle, and let that for the calcium salt be the left 

 side. The right side will then be the base line for the magnesium 

 salt, Each of these three base lines represents a row of solu- 

 tions each having one-eighth of its total volume-molecular con- 

 centration due to the salt for which the line is named. The apex 

 opposite this lipe represents a solution in which six-eighths are 

 due to that salt. The volume-molecular proportions of all three 

 salts are quickly determined for any solution represented on the 

 diagram. The diagram is given herewith. To designate the 

 solutions, the rows on the 

 diagram are numbered R6 



from below upward, and 

 the solutions are numbered 

 in each row from left to 

 right. To refer to a solu- 

 tion we first write the 

 Roman numeral denoting 

 the type (what three salts 

 are used), then we write 



the row number (preceded , , , , , 



by the letter R), then we SI S2 S3 S4 S5 S6 

 write the solution number 



26 



