Jan. 3, igao Relation of Moisture in Svbstrata to Salt Balance 369 



the factor under investigation. It appears that correct interpretations 

 of the influence upon plant growth of such variables as the relative salt 

 proportions here considered are not possible unless the moisture supply 

 of the substratum in which the plants are rooted is maintained within 

 very narrow variation limits. 



YIELDS OF ROOTS 



The position of the group of nine cultures which produced the highest 

 average dry-weight yields of roots in each series is indicated by the shaded 

 areas on the triangular diagrams of figure 3. This diagrammatic arrange- 

 ment is in every respect similar to that of figure i , which shows the dis- 

 tribution of high top yields. A comparison of the triangular diagrams 

 of figure 3 shows the agreements between areas marking high root yields 

 to be even more pronounced than are those between the corresponding 

 areas representing the high yields of tops. Out of a total of nine cultures 

 in each series which produced high yields of roots, five are corresponding 

 cultures of the three series, as is indicated on the diagrams. These cul- 

 tures are R4C4, R5C2, R5C3, R5C4, and R6C3. It will be observed also 

 that eight corresponding cultures are represented in the areas of high 

 root yields in both series A and series B. The highest yield of roots in 

 each of these two series was obtained from culture R4C5, while in series 

 C the highest yield was produced by culture R5C4. 



Series A and series B, with low and medium moisture contents, respec- 

 tively, show almost absolute agreement with respect to the location of 

 the areas of high root yields. These areas occupy central positions on 

 the right margins of the diagrams, while the corresponding area on the dia- 

 gram of series C, with the highest moisture content, is shown to occupy 

 a region on the right and left margins of the triangle, farther from the 

 base and extending to the apex. It is thus evident that there is scarcely 

 any shifting of the physiological balance of salt proportions for the group 

 of nine cultures giving the highest yields of roots in passing from the low 

 to the medium moisture content, but with the highest moisture content 

 the physiological salt balance characterizing the nine high-yielding cul- 

 tures shows the same tendency to migrate toward the apex of the triangle 

 as did that of the nine cultures which produced high yields of tops in 

 the same series. But this shifting of the physiological salt balance char- 

 acterizing good yields of roots, with a change from the low to the high 

 moisture content, is scarcely more pronounced than is that of the salt 

 balance characterizing good top yields, since the same number of high 

 root yields as of high top yields in each group of nine occurred with 

 corresponding cultures in the three series. 



