334 EAUL S. JOHNSTON 



The solutions employed had an osmotic pressure of one atmos- 

 phere and contained the following salts; monobasic potassium 

 phosphate, calcium nitrate and magnesium sulphate. In the 

 triangular arrangement of the twenty-one culture solutions chosen 

 by the Committee on Salt Nutrition of Plants 4 the three at the 

 apices of the outer triangle and the three at the apices of an 

 inner triangle were the ones used in this work. These culture 

 solutions are designated as R1S1, R1S6, R2S2, R2S4, R4S2 and 

 R6S1 of type I and their positions are shown in the diagram of 

 figure 4. 



KH 2 P0 4 

 Fig. 4. Position of six selected solutions on triangle of 21 solutions. 



The cultures were continued for thirty days after which the 

 green and dry weights were determined. The green weights 

 were also determined at the time the plants were placed in the 

 solutions. At the end of the second and third ten-day periods 

 transpiration measurements were obtained. The results of this 

 experiment are given in tabular form in table 1. Averages of 

 three plants are considered except where otherwise indicated by 

 small superscript figures. 



4 See "Salt requirements of representative agricultural plants." Science n.s. 

 49: 143. 1919. See also the specially prepared plans obtained from the chairman 

 of Committee on Salt Requirements of Plants, Laboratory of Plant Physiology, 

 The Johns Hopkins University, Baltimore. 



