30 NOURISHMENT OF PLANTS. 



JVon-azotized Substances. Azotized Substances. 



Gum and Dextrine, Chlorophyll, 



Sugar, Vegetable Bases, etc. 



Fat and Oil, 

 Resin, 

 Vegetable Acids, etc. 



In all plants, however, certain inorganic constit- 

 uents^ in small quantity, partly dissolved in the sap, 

 and partly deposited in the cells, are also found. These 

 are called the mineral constituents of vegetables, be- 

 cause they are derived from the mineral substances 

 contained in the ground or soil. They may also be 

 denominated incombustible , because they are not 

 burnt up or volatilized by heat; or ashy, because 

 upon the combustion of the plant they remain be- 

 hind as ashes. They are distinguished from the 

 organic constituents by being incapable of putres- 

 cence or decay. 



It was formerly supposed that these constituents 

 were unimportant to plants, and that their existence 

 in them was due to the accidental circumstance of 

 their dissolution in the water contained in the soil, 

 and subsequent introduction into the organism of 

 the plant. That this assumption is nevertheless 

 entirely erroneous must be inferred at once from the 

 consideration, that we can powerfully promote and 

 hasten the growth of vegetables by a superficial cov- 

 ering of gypsum, lime, ashes, salt, or other mineral 

 ingredients, and any thing which furthers and ac- 

 celerates their growth cannot be unimportant to 

 plants. It is .now positively known that vegetables 



