SECT. IV. SALTS. 71 



presume that salts are also taken up by the roots of 

 plants vegetating even in their natural habitats. 



But if salts are thus taken up by the root of the Whether 



1*1 



vegetating plant, does it appear that they are taken f ' e d get 

 up as a food ? Some plants, it must be confessed, are 

 injured by the application of salts, as is evident from 

 the experiments of Saussure; but others are as 

 evidently benefited by it. Trefoil and Lucern have 

 their growth much accelerated by the application of 

 sulphate of lime, though many other plants are not 

 at all influenced by its action. The Parietaria 

 Nettle, and Borge, will not thrive except in such 

 soils as contain nitrate of lime or nitrate of potass : 

 and plants inhabiting the sea coast, as was observed 

 by Du Hamel, will not thrive in a soil that does 

 not contain muriate of soda. 



It has been thought, however, that the salts are 

 not actually taken up by the root, though converted 

 to purposes of utility by acting as astringents or 

 corrosives in stopping up the orifices of the vessels 

 of the plant, and preventing the admission of too 

 much water : but it is to be recollected that the 

 salts in question are found 'by analysis in the very 

 substance of the plant, and must consequently have 

 entered in solution. It has been also thought that 

 salts are favourable to vegetation only in proportion 

 as they hasten the putrefaction of vegetable sub- 

 stances contained in the soil, or attract the humidity 

 of the atmosphere. But sulphate of lime is not 

 deliquescent ; and if its action consist merely in 



