THE PL.1NT. 31 



acid, this substance has the power of coinbining witli 

 auj of the alkalies. Its most important compound 

 is formed with lime. 



Phosphate of lime forms about 65 percent, of the 

 dry weight of the bones of all animals, and it is all 

 derived from the soil tlirough the medium of plants. 

 As plants are intended as food for animals, nature 

 lias provided that thej shall not attain their perfec- 

 tion without taking up a supply of phosphate of 

 lime as well as of their other eartlij ingredients ; 

 consequently, there are many soils which will not 

 produce good crops, simply because they are deficient 

 in phospliate of lime. It is one of the most impor- 

 tant ingredients of manures, and its value is depen- 

 dent on certain conditions which will be hereafter 

 explained. 



Another use of phosphoric acid in the plant is to 

 supply it with the small amount of jphosphorus^ 

 which seems to be required in the formation of the 

 seed. 



SULPnUKIC ACID. 



Sulphuric acid is important to vegetation, and its 

 addition to the soil often renders it more fertile. It 

 is composed of sulphur and oxygen, and is made for 

 manufacturing purposes, by burning sulphur. With 

 lime it forms sulphate of lime, which is gypsum or 

 "plaster." In this form it is often found in na- 

 ture, and is most extensively used in agriculture. 

 The methods for supplying sulphuric acid will bo 

 described hereafter. It gives to the plant a small 



