SET. IV. SALTS. 6 



SECTION IV. 



Salts. 



MOST plants are found by analysis to contain a 

 certain proportion of salts such as nitrate, muriate, 

 and sulphate of potass or soda as has been already 

 shown. How do plants acquire them ? In the 

 earlier periods of phytological investigation., when 

 every effect was attributed to the agency of the 

 vital principle as exerted upon the air and water 

 which the plant inhales or absorbs, it was thought 

 that the salts contained in vegetables are formed in 

 the process of vegetation : but this is also one of 

 those extravagant conjectures of which further re- 

 search has exposed the absurdity. The salts which Absorbed 

 have been detected in vegetables are known to exist tion. 

 in the soil. It is most likely therefore that the root 

 absorbs them in solution with the water by which 

 the plant is nourished. It is at least certain that 

 plants may be made to take up by the roots a con- 

 siderable proportion of salts in a state of artificial 

 solution. M. Saussure prepared ] different solutions, 

 consisting each of 40 cubic inches of distilled water, 

 together with 12 grains of the peculiar salt or other 

 substance on which the experiment of absorption was 

 to be made. The first solution contained muriate of 

 potass ; the second, muriate of soda ; the third, 

 muriate of lime ; the fourth, sulphate of soda ; the 



