64 



Lime is another prominent constituent of the 

 ashes of plants. While it varies from 7 to 12 per 

 cent, in cereals and root crops, it is found in 

 large quantities in all leguminous plants, as pease, 

 beans, &c., in the ashes of which it is present to the 

 extent of 30 per cent. Tobacco is also essentially 

 a lime plant. 



Magnesia is always found more or less present 

 with lime, and either seems capable of taking the 

 other's place ; they form part of the soil in com- 

 bination with carbonic, sulphuric, and phosphoric 

 acid ; and as these salts are insoluble in pure water, 

 but are taken up in small quantities by water con- 

 taining carbonic acid, we see here one of the reasons 

 why the presence of decomposing vegetable matter 

 in the soil tends to a most luxuriant growth of crops. 



Lime seems to have a similar duty to 

 fulfil in vegetable as it has in animal life ; it 

 supplies, conjointly with Silica, the necessary 

 strength to the cellular tissue ; it forms the bones 

 of vegetable life, just as it forms, in combina- 

 tion with phosphoric acid, the bones of animal 

 life. 



Sulphuric Acid is generally found in the soil in 

 combination with lime, from which plants extract 

 the quantity necessary for their existence. 



The last of the inorganic elements which it 

 is necessary to consider is a mineral acid 

 Phosphoric Acid. When we incinerate the seeds 



