Of that we have an instance in the hyacinth and other bulbous roots, which will grow and blossom beautifully in glasses of water. But I confess I should think it would be difficult to rear trees in a similar manner.
MRS. B.
No doubt it would, as it is the burying of the roots in the earth that supports the stem of the tree. But this office, besides that of affording a vehicle for food, is far the most important part which the earthy portion of the soil performs in the process of vegetation; for we can discover, by analysis, but an extremely small proportion of earth in vegetable compounds.
CAROLINE.
But if earths do not afford nourishment, why is it necessary to be so attentive to the preparation of the soil?
MRS. B.
In order to impart to it those qualities which render it a proper vehicle for the food of the plant. Water is the chief nourishment of vegetables; if, therefore, the soil be too sandy, it will not retain a quantity of water sufficient to supply the roots of the plants. If, on the contrary, it abound too much with clay, the water will lodge in such quantities as to threaten a decomposition of the roots. Calcareous soils are, upon the whole, the most favourable to the growth of plants: soils are, therefore, usually improved by chalk, which, you may recollect, is a carbonat of lime. Different vegetables, however, require different kinds of soils. Thus rice demands a moist retentive soil; potatoes a soft sandy soil; wheat a firm and rich soil. Forest trees grow better in fine sand than in a stiff clay; and a light ferruginous soil is best suited to fruit-trees.
CAROLINE.
But pray what is the use of manuring the soil?
MRS. B.