

ROOT HAIRS AND GROWTH 



367 



hydrogen ion concentration, molar con- 

 centration, and rate of elongation. 



The lowest molar concentration of 

 calcium choride (16) studied thoroughly 

 was 0.008. It gave a pH range from 5.9 



of o.oz8 M had a range of 3.9 to 10.4, 

 with optima at 6.5 and 9.0, the alkaline 

 optimum in this case being the greater, 

 while at lower concentration of the salt 

 it was the lesser. In 0.060 M the range is 







Fig. 6. A Model Showing Graphs Similar to Those Given in Figure 5 Disposed upon a Plane at Distances 

 Coordinate with the Molar Concentrations 

 The graphs here used are based upon the most rapid root hair measured, rather than on the average. The 

 result is not substantially different, except that no median minimum is apparent in 0.008. This model shows 

 that the optima and the median minima fall in approximately straight lines. 



to 1 1.4 with a distinct optimum at pH 3.5 to 9.5, with the lesser optimum at 4.5 



8.0 and a lower and less distinct optimum and the greater at 8.5. In o.izo M 



at 10. o (fig. 5). A concentration of calcium chloride the range is 6.0 to 9.0 



o.ozo molar gave a range of 3.4 to 11. 4 with just one Optimum at 7.0. 



with optima at 7.0 and 9.0. A solution It is apparent that these data can be 



