192 ORIGIN OF ORGANIC MATTER 



bark, opium, and the potato plant, are always large in an inverse 

 ratio to the small amount of mineral bases which they contain. 



However restricted may be the sense in which we interpret 

 many of Liebig's propositions, it is most clearly apparent, from all 

 exact examinations of vegetable ashes, as well as from the careful 

 observations of the influence of individual salts as manures, that the 

 alkaline carbonates and their phosphates are of the highest import- 

 ance in the different processes in the life of plants. It would carry 

 us too far from the scope of our inquiries, were we to enumerate all 

 the facts relating to this subject, with which we have been long 

 acquainted ; and we will therefore content ourselves with referring 

 to some few of the results which have been obtained from E. Wolff's 

 admirable investigation of the mineral constituents of the horse- 

 chesnut. The carbonate of lime predominates in the bark and in 

 the wood, whilst the fruit and leaves contain far more carbonate of 

 potash than the bark and wood. Phosphoric acid is most abundant 

 in the flower-stalks and kernels, whilst sulphuric acid and silica 

 predominate in the leaves. In the horse-chesnut, very simple 

 ratios exist between the quantities of oxygen in the bases com- 

 bined with carbonic acid in the different parts of the plant (the 

 carbonates being calculated for 100). The quantity of oxygen 

 in 100 parts of the alkaline carbonate from the ash of the bark 

 amounted to 27, that from the wood and leaves to 24, that from the 

 leaf-stalks and brown husks of the ripe fruits to 21, and that from 

 all the other parts of the plant which were examined to 18, which 

 corresponds with the simple arithmetical progression of 9:8:7:6. 

 Wolff found that the ratio between the soluble and the insoluble 

 constituents was very simple in all parts ; thus, for instance, it was 

 as 4:6 in the fluid circulating between the wood and the bark, and 

 the same in the leaves, while on the other hand it was as 3:7 in 

 the newly formed wood, and as 6:4 in the leaf-stalks, while in the 

 flower-stalks it was as 2:9, and in the interior of the kernels of 

 the ripe fruit as 2:7. Of all the mineral substances, sulphate of 

 potash predominated in the leaves, and this was more especially 

 the case in the spring, at the season of blossoming, whilst at the 

 same period the juice of the bark and wood contained no trace of 

 sulphuric acid. The ash of the leaves was very rich in insoluble 

 phosphates, whilst that of the blossoms and fruit contained a larger 

 amount of the soluble phosphates. 



It is quite unnecessary to enter more fully into the question of 

 the influence exerted by the alkaline and earthy carbonates, sul- 

 phates, and phosphates, upon the growth of plants as manure, for 



