ACTION OF THE SOIL ON PLANTS. 151 



quire it, which live in water, whence they derive their 

 nourishment : but this class is very insignificant. The 

 earth affords both support and nourishment to plants 



Caroline. Or should you not rather say, is the vehicle 

 of their nourishment, since their food is composed princi- 

 pally of animal and vegetable remains ? 



Mrs. B. Very true ; the various saline particles which 

 plants pump up from the soil, should rather be considered 

 as flavoring their food, than forming a nutritive part of 

 it : their daily bread is of animal and vegetable origin. 



Caroline. And when there is a deficiency of salts to 

 flavor their food, have not plants the power of forming 

 them in their internal laboratory ? 



Mrs. B. No ; the chemical apparatus of their organs 

 is so arranged that it can elaborate only vegetable juices, 

 and is as incapable of forming a salt or an oxide, as an 

 animal is of forming the phosphat of lyme with which its 

 bones are indurated. 



Emily. How then are these salts, which are composed 

 of various ingredients, formed ? 



Mrs. B. The metals intermixed with the earths of 

 which our globe is composed attract oxygen from the at- 

 mosphere, and combine with it ; and it is thus that the 

 mineral kingdom prepares the oxides, for the use of or- 

 ganised bodies. 



The earth, we have said, supports plants, and gives 

 them a fulcrum or point of rest, which animals have not, 

 because they do not require it. In order to support plants, 

 the ground must be neither too compact nor too loose. 

 They cannot grow upon a hard rock, nor in a moving 

 sand : their roots cannot penetrate the first, nor take firm 

 hold on the latter. 



Emily. Besides, a plant would find no food to nour- 

 ish it on a barren rock. 



Mrs. B. That most patient and persevering of agri- 

 culturists, Nature, teaches us how to prepare a soil, even 

 on the hard rock, or the sterile lava of a volcano : she 

 commences her operations on these obdurate bodies by 



834. And of the saline particles which the plants receive from the soil! 

 835. Caroline asks, if plants have the power of forming salts vyhat is 

 the answer 1 836. How does the mineral kingdom prepare oxides for 

 the use of organized bodies'! 837. What is said of the ground in or- 

 der to give support to plants 1 



