TRUE & HARVEY: ABSORPTION OF CALCIUM SALTS 509 



Table 2 



Net Absorption by Squash Seedlings from Solutions of Calcium Sulphate 



Original Concentration Minimum Concentration Maximum Absorption 



as Grm. Norm. as Grm. Norm. as Grm. Norm. 



CaS04 Xio-6 CaS04Xio-6 CaSOiXio-e 



4-9 43-6 - 387 



11.08 61.4 — 49.32 



15-6 50.0 - 34.4 



31-3 27.9 + 3-4 



52.1 37-7 144 



loi .9 76.0 25.9 



1494 92.0 574 



197-5 146.2 51-3 



319-1 251.5 57.6 



414-1 335-3 78-8 



535-4 448-1 87.3 



654-4 528.7 125-7 



727.6 615.6 112.0 



824.4 704.6 1 19.8 



Calcium Chloride 



In the foregoing experiments we have had to do with salts in which 

 both cation and anion are required for the normal growth of higher 



plants, and we find squash seedlings behaving toward them in sharply 



+ + - - 



contrasting ways. From solutions containing Ca and NO3 ions root 



+ + — 



absorption is very active. When Ca ions are accompanied by SO4 

 ions, however, absorption is relatively small. 



In view of these facts it is a matter of no small interest to test the 

 behavior of plants in solutions in which the Ca ion is accompanied by 

 the CI ion. 



A series of solutions was made up containing a graded series of 

 concentrations running up to 582.4 grm. norm, in a million liters. 

 The experiment ran from Aug. 9 to Aug. 26, 191 6. A graphic record 

 of the concentration changes observed is shown in the accompanying 

 group of curves (Fig. 3). It is perhaps hardly necessary to do more 

 than to point out certain of the more important features to be observed. 

 In general a very striking similarity to the corresponding set of curves 

 obtained from Ca(N03)2 solutions may be noted. The solutions hav- 

 ing an original concentration of 32.5 and less show a loss of electrolytes 

 for the first five or six days after which time absorption begins and 

 continues until near the end of the experiment, but in none is the 

 loss during the early days fully regained, although in that originally 

 containing 32.5 grm. norm, the net loss is practically negligible. 

 At this concentration we find again evidence of a critical concentration 

 of some sort below which the plants can not absorb and above which 



