62 



ashes in a plant when life and growth are most 

 vigorous, and that this percentage diminishes as 

 the plant approaches perfection ; the balance, 

 therefore, must have been returned to the soil, after 

 fulfilling its function of acting as a solvent medium 

 for such minerals as are insoluble by themselves. 



I will mention two instances in which this differ- 

 ence has been remarked. An analysis of an entire 

 plant of sunflower showed before flowering 14*7 

 per cent, of ashes, while when bearing seed it 

 contained only 9*3 per cent, of inorganic substances. 

 And a wheat plant gave 7*9 per cent, of ashes 

 before flowering, and 3*3 per cent, when bearing 

 the ear. What other conclusion, then, can be 

 drawn, but that the balance was only employed 

 as a solvent, and was returned to the soil when no 

 longer required ? 



Some idea may be formed of the rapid circulation 

 of sap in plants by a reference to the careful experi- 

 ment made by Mr. J. B. Lawes of Rothamstead, 

 the celebrated patent manure-maker, who, as men- 

 tioned in a previous chapter, has shown that, for 

 every grain of mineral matter fixed in the plant, 

 two thousand grains of water have to pass through 

 its system. This explains the presence of some 

 minerals which are found in plants, such as iron 

 and manganese, for which potash and other alkalis 

 do not act as solvents. 



It is now known that all substances, even gold, 



