Jan. 2, 1920 Relation of Moisture in Substrata to Salt Balance 361 



DISCUSSION OF RESULTS 

 YIELDS OF TOPS 



For convenience in presenting the data, the three series of cultures 

 here considered will be designated series A, series B, and series C, accord- 

 ing as the cultures of the series were maintained at a moisture content 

 of 40 per cent, 60 per cent, or 80 per cent of the water-retaining capacity 

 of the sand. Since this triple series of cultures was repeated, two corre- 

 sponding dry-weight measurements of both tops and roots are available 

 for each culture; and by combining these, the average numerical data 

 given in the tables were obtained. 



Table I presents the average dry-weight yields of tops for each of the 

 three moisture contents employed. The first column of each section 

 gives the average absolute yield values in grams, while the second column 

 gives the weights of tops relative to the weights from the first culture 

 (RiCi) taken as unity. These relative dry- weight values were obtained 

 by averaging the corresponding relative yield values from the two triple 

 series, conducted during different time periods. Each of these relative 

 data is, therefore, the average of two ratios and not the ratio obtained by 

 dividing its corresponding average absolute dry-weight value by the 

 average absolute value of the first culture (RiCi) in the same series. It 

 thus happens that the relative values given in the table do not always 

 bear exactly the same relation to each other as do the absolute values. 

 The average relative data obtained from the group of cultures which 

 produced the nine highest yields in each series (upper one-fourth) are 

 shown in the table in italics, excepting the highest relative yield value of 

 each series which appears in bold-face type. The culture numbers refer 

 to the positions which the cultures occupy on the triangular diagrams 

 graphically representing the variations in salt proportions and partial 

 osmotic concentrations of the solutions added to the sand cultures.* 



• For descriptions of this triangular diagramatic scheme see Shive {12), McCall (9), and Hibbard ('5). 

 An excellent discussion of the triangle system and its use in problems of plant nutrition has recently been 

 published by Schreiner and Skinner {11). 



