320 PROPERTIES OF THE COLLOIDAL CONSTITUENTS 



sodium chloride and lead acetate, sodium chloride and aluminium sul- 

 phate, sodium chloride and chromium sulphate, potassium chloride and 

 calcium nitrate and, in fact, some measure of mutual antagonism is 

 usually but not invariably found to subsist between every pair of inor- 

 ganic salts. 



Very striking examples of the mutual antagonism of inorganic 

 salts are afforded by the experiments of Osterhout upon plant-tissues. 

 The following shows the aggregate length of roots produced after sixty 

 days by wheat-seeds allowed to germinate in various salt solutions of 

 2^ molecular concentration. 



Aggregate length 

 Solution. of roots mm. 



Sodium chloride . . . ' . . " . .'. . . . 59 



Potassium chloride . . ., . . ''. 68 



Magnesium chloride .-.:'.. 7 



Calcium chloride 70 



1000NaCl+ 10CaCl 2 . . . . ; 254 



lOOONaCl + 22KC1 + 10CaCl 2 324 



1000 NaCl + 78MgCl 2 + 10CaCl 2 377 



1000 NaCl + 78MgCl 2 + 38MgSO 4 + 22KC1 + 10CaCl 2 . . . . . 360 

 Distilled water 740 



Since the roots exhibit a maximum growth in distilled water the 

 various salts are evidently not required for the nutrition of the plants. 

 The individual salts in pure solution are all highly toxic as compared 

 with distilled water, but mixtures of the salts in proportions approxi- 

 mating to those found in sea-water permit very extensive growth 

 of roots to occur. The following data show the percentage-increase in 

 the length of the thallus which develops from the seeds of Equisetum 

 in various salt solutions of T f ^ molecular concentration. 



Percentage increase 

 in length of thallus 

 Solution. after 50 days. 



Sodium chloride . . . 



Potassium chloride 



Magnesium chloride 



Calcium chloride 700 



lOOONaCl + 22KC1 



lOOONaCl + 78MgCl 2 40 



lOOONaCl + 78MgCi 2 + 22KC1 40 



lOOONaCl + 10CaCl 2 980 



lOOONaCl + 22KCI + 10CaCl 2 . 1500 



lOOONaCl + 78MgCl 2 + 10CaCl 2 1760 



lOOONaCl + 78MgCl 2 + 38MgSO 4 + 22KC1 + 10CaCl 2 ... 1500 

 Distilled water 1760 



In certain instances the toxicity of such a universally distributed 

 substance as sodium chloride may be extremely great. Thus Osterhout 

 found specimens of Vaucheria which were killed within a few days by 

 so small a concentration as y^^ sodium chloride, although the running 

 water in which these algse were growing contained no less than twelve 

 times this concentration of sodium chloride. In the brook, however, 

 the toxicity of the sodium chloride was completely annulled by the 



