60 



Potash and Soda have long been known to form 

 a considerable portion of the mineral constituents 

 of plants. Potash is the more important of the 

 two, Soda preponderating only in plants which 

 exist on sea-shores, from the ashes of which we 

 formerly derived all our Carbonate of Soda. 

 Potash is the alkali essential to most of our crops, 

 and constitutes a large percentage of the ashes of 

 every plant on the average fully 30 per cent. It 

 is always found present in greater proportion in the 

 ashes of leaves and stalks than in those of 

 grains ; and while forming nearly 40 per cent, of 

 the ashes of leaves, it constitutes only 20 per cent, 

 of the ashes of the grains of cereals. 



The functions which potash performs in vegetable 

 life are not sufficiently studied as yet ; but as, by 

 chemical experiments, it is known that potassa will 

 change woody fibre into different organic acids, as 

 acetic, oxalic acid, &c., we may fairly suppose that it 

 has similar duties to perform within the cells of the 

 plant ; while it is absolutely indispensable for bring- 

 ing the silica, so essential to the growth of cereals, 

 into a state of solution, to be carried through the 

 cells of vegetable life for assimilation. It must be 

 remembered that not a grain of an inorganic 

 substance can enter the system of a plant unless 

 dissolved by the medium of water ; otherwise, 

 not the thousandth part of a grain of solid substance 

 could enter into the absorbing cells of the root ; and 



