414 CHEMICAL ELEMENTS. PART 11. 



bonic acid, water and ammonia : these they have the 

 power of decomposing, and recombining their simple 

 elements into new compounds. Carbon forms the hard 

 part of plants, and enters extensively into their most 

 delicate structure; but it is never found free. Com- 

 bined with hydrogen and oxygen it not only constitutes 

 the cell wall cellulose, which may be regarded as the 

 skeleton of the vegetable world, but hundreds of com- 

 pounds differing decidedly in their properties, yet con- 

 sisting only of these three elements united with one 

 another in different quantities and proportions. Pro- 

 teine, a compound of all the four simple elements, is a 

 mucilaginous substance, which lines the primordial cell, 

 is homogeneous at first, and afterwards more or less 

 granulated. It is present wherever the vital energy is 

 in activity. 



Although these four primary elements form the basis 

 of vegetation, plants require other substances which 

 they absorb from the ground in a state of solution, 

 such as silex, or rather silicious salts having a base of 

 potash or soda, the carbonates, sulphates, and phos- 

 phates of lime, the phosphate of manganese, and the 

 oxides of manganese and iron, with various other metals 

 and substances in a state of combination and solution. 

 A few are universal constituents, as the earths and alka- 

 lies ; in general each race of plants only absorbs such as 

 ^re peculiar to itself. Soda abounds in the Algse and 

 is found in the Liliacese, Cruciferse, and other plants that 

 are indigenous on the sea-coast, or in brackish marshes. 

 Potash exists in land plants, and cannot be replaced by 

 soda, for however rich the soil may be in soda, they do 

 not thrive in it. The ashes of land plants consequently 

 contain the metal potassium, while most of the Algae 

 yield sodium ; they also yield chlorine, iodine, and bro- 

 mine in a state of combination. It is proved by spec- 

 trum analysis, that every plant, with the exception of 



