Nor is it more difficult to see how starch may be converted into sugar, and this again into woody fibre; or how, again, sugar may be converted into starch in the ear of corn, or woody fibre into sugar during the ripening of the winter pear after its removal from the tree. Any one of these substances may be represented by carbon and water only.

Thus,—

50 lbs. of carbon with50of water, make100 of woody fibre.
50 lbs.37½  87½ of ulmic acid.
of cane sugar,
50 lbs.72½ 122½of starch, or
of gum.
50lbs.56 106 of vinegar.

In the interior of the plant, therefore, it is obvious that, whichever of these substances be present in the sap, the elements are at hand out of which any of the others may be produced. In what way they really are produced, the one from the other, and by what circumstances these transformations are favoured, it would lead into too great detail to attempt here to explain.[6]

We cannot help admiring to what varied purposes in nature the same elements are applied, and from how few and simple materials, substances, the most varied in their properties, are in the living vegetable daily produced.

CHAPTER IV.

Of the Inorganic Constitution of Plants—Their immediate Source—Their Nature—Quantity of each in certain common Crops.

SECTION I.—SOURCE OF THE EARTHY MATTER
OF PLANTS—SUBSTANCES OF
WHICH IT CONSISTS.

When plants are burned, they always leave more or less of ash behind. This ash varies in quantity in different plants, in different parts of the same plant, and sometimes in different specimens of the same kind of plant, especially if grown upon different soils; yet it is never wholly absent. It seems as necessary to their existence in a state of perfect health as any of the elements which constitute the organic or combustible part of their substance. They must obtain it therefore along with the food on which they live: it is in fact a part of their natural food, since without it they become unhealthy. We shall speak of it therefore as the inorganic food of plants.