CONTENTS. xiii 



CHAPTER III. 



THE INORGANIC PARTS OP PLANTS. 



The small percentage of the inorganic parts of the plant when 

 compared with the organic parts. The functions of the 

 former with regard to the latter. The importance of 

 inorganic parts in the vegetable kingdom. Vegetable life 

 cannot exist in the absence of any one of their number. 

 The ashes of different plants vary in their composition. The 

 importance of analyses. Potash and soda. Their func- 

 tions in vegetable life. Potash a solvent for silica. The 

 same amount of potash serves to dissolve many times its 

 maximum of silica by repeated circulation through the 

 system of the plant. Mr. Lawes' experiments on the 

 circulation of the sap and the quantity of inorganic matter 

 deposited. Silica and sand. Lime a prominent consti- 

 tuent of root-crops and leguminous plants. Magnesia. 

 The property of lime and magnesia to take each other's 

 places. Lime and silica form the bones of vegetable life. 

 Sulphuric acid. Phosphoric acid. Phosphoric acid 

 forms the principal mineral constituent of the seed. No 

 grain can be formed in its absence. The gradual reduc- 

 tion of its percentage in the soil affects chiefly the outturn 

 of the seed. The Indian method of cultivation has 

 deprived the soil of this important substance in far greater 

 proportion than of any of the other inorganic parts. No 

 restoration has been made for the loss occasioned by the 

 annual withdrawal of the grain crops. Where is all the 

 phosphoric acid gone to ? The export trade of bones 

 deprives India of the means to repair the waste of past 

 generations. The value of bones as manure. The percen- 

 tage of phosphoric acid in rice. The estimated quantity 

 withdrawn from an acre by a cultivation extending over 

 two thousand years. The deficiency of phosphoric acid in 

 the soil of India proved by analysis. The small average 

 outturn due to this deficiency. The quantity of phosphoric 

 acid required by the rice-plant, and the quantity available. 



