62 



rishment from the soil, consequently incapable of de- 

 veloping a sufficient foliage/* and therefore unable to 

 digest and elaborate even the scanty sap that is sup- 

 plied to them. 



The reason of the sap becoming unnaturally saline 

 appears to be, that in proportion as the vigour of any 

 vegetable declines, it loses the power of selecting by 

 its roots the nourishment congenial to its nature. M. 

 Saussure found, in his experiments, that the roots of 

 plants, growing in saline solutions, absorbed the most 

 of those salts that were injurious to them, such as 

 sulphate of copper, evidently because the declining 

 plant lost the sensitiveness and energy necessary to 

 select and to reject. 



M. Saussure also found, that, if the extremities of 

 the roots were removed, the plants absorbed all solu- 

 tions indiscriminately, f 



An ungenial soil would have a debilitating influence 

 upon the roots in a proportionate, though less violent, 

 degree than the sulphate of copper, and as these, con- 

 sequently, would absorb soluble bodies more freely, 

 and without that discrimination so absolutely neces- 

 sary for a healthy vegetation, so the other most essen- 

 tial organs of nutrition, the leaves of the weakened 



* No symptom of a cankered tree is more invariable than a 

 deficiency of leaves. 



f Saussure's Recherches Chimiques sur la Vegetation, 260. 



