92 OF THE INORGANIC 



putrefaction. All the innumerable products of 

 vitality resume, after death, the original form from 

 which they sprung. And thus death the complete 

 dissolution of an existing generation becomes the 

 source of life for a new one. 



But another question arises, Are the conditions 

 already considered the only ones necessary for the 

 life of vegetables ? It will now be shown that they 

 are not. 



OF THE INORGANIC CONSTITUENTS OF PLANTS. 



Carbonic acid, water and ammonia, are necessary 

 for the existence of plants, because they contain 

 the elements from which their organs are formed ; 

 but other substances are likewise requisite for the 

 formation of certain organs destined for special 

 functions peculiar to each family of plants. Plants 

 obtain these substances from inorganic nature. In 

 the ashes left after the incineration of plants, the 

 same substances are formed although in a changed 

 condition. 



Many of these inorganic constituents vary ac- 

 cording to the soil in which the plants grow, but a 

 certain number of them are indispensable to their 

 development. All substances in solution in a soil 

 are absorbed by the roots of plants, exactly as a 

 sponge imbibes a liquid, and all that it contains, 

 without selection. The substances thus conveyed 

 to plants are retained in greater or less quan- 



