510 



BROOKLYN BOTANIC GARDEN MEMOIRS 



they are able to do so. This required minimum quantity is probably 

 of considerable physiological significance. At higher initial con- 

 centrations, from 53.5 to 384.0 grm. norm, loss of ions during the 

 early days of the experiment becomes less marked as the concentration 

 increases. Absorption usually begins more promptly and proceeds with 

 greater speed as the quantity of ions present increases until in all cases 

 but one the concentration of ions remaining in the solution is reduced 



650 



(00 



Squash CaCL I8°c. 



650 

 600 

 550 

 500 

 450 



700 



4 5 e 7 Q 9 10 II 12 13 

 Fig. 3. For explanation see text. 



to the unabsorbable minimum at an average concentration of approxi- 

 mately 27 grm. norm. X lO"*^. Only when the original concentration 

 of 582.4 grm. norm. X io~^ is reached do we find the quantity of ions 

 offered greater than can be reduced by the seedlings to the unab- 

 sorbable minimum. These relations are seen in the numerical data 

 given in Table 3, in which the concentration relations are shown as 

 they exist at the time of maximum absorption. Here again the 

 similarity to the situation seen in solutions of Ca(N03)2 is striking. 



If we are justified in concluding that the depressing action of the 

 SO4 anion is responsible for the great reduction of root absorption 



