Jan. 2, 1920 Relation of Moisture in Substrata to Salt Balance 367 



of each series, taken from the columns of Table I, were arranged in the 

 descending order of the values obtained from series B, employing a 

 medium moisture content. These values were then plotted to form the 

 three graphs shown in figure 2, representing the three different series of 

 absolute dry-weight values. The continuous line marked by large dots 

 and sloping somewhat uniformly downward to the right represents 

 series B, with medium moisture content, while the broken line and the 

 plain continuous line represent the 3delds obtained from the series with 

 the highest and the lowest moisture contents, respectively. 



Inspection of figure 2 shows that each of the three graphs has a de- 

 cided tendency to slope downward to the right, thus indicating, in a 

 general way, changes in the growth rates with variations in the salt 

 proportions. In this respect the three series show a general agreement, 

 which was brought out also by the triangular diagrams. The graph 

 representing the series with medium moisture content lies above the 

 other two graphs throughout most of its length. In the upper third of 

 its course this graph shows the average absolute yields to be much 

 higher than the corresponding yields from the other two series. How- 

 ever, that portion of the graph representing medium and low yields is 

 intersected at various points by the other graphs. Nine yields from 

 series A, with lowest moisture content, and three yields from series C, 

 with highest moisture content, are thus shown to have higher values 

 than the corresponding yields from series B. 



The graphs of series A and series C are quite irregular and show little 

 tendency toward parallelism. Practically the only tendency toward 

 any agreernent, in this respect, between these 2 series is shown for the 

 first 5 cultures, which appear to rise and fall simultaneously. It will be 

 observed, however, that more than two-thirds of the yields from series 

 A are higher than the corresponding yields from series C. The highest 

 yield from series C is lower than the highest from series A, and both are 

 considerably lower than the highest yield from series B. In fact, the 

 first 12 cultures of series B, as these cultures are arranged for the graphs 

 of figure 2, show yield values which are considerably above the corre- 

 sponding yield values of the other 2 series. This is somewhat striking 

 in connection with the fact that series A and series C represent the ex- 

 tremes in the moisture content employed. 



Perhaps the most important point brought out by the foregoing consid- 

 eration of the absolute dry-weight values is the fact that the differences 

 in the growth rates brought about by the variations in the moisture 

 content, as indicated by the differences in the yield values of the corre- 

 sponding cultures of the three series, are nearly as marked as are the 

 differences in the rates of growth resulting from variations in the salt 

 proportions throughout each series. This emphasizes the importance 

 of a constant moisture supply in all pot-culture work of this kind, where 

 the influence of relative salt proportions* or of fertilizer treatments is 

 153425°— 20 3 



