There are none so little skilled in regard to the capabilities of the soil, as not to be aware that some lands naturally produce abundant herbage or rich crops, while others refuse to yield a nourishing pasture, and are deaf to the often repeated solicitations of the diligent husbandman. There exists, therefore, a universally understood connection between the kind of soil and the kind of plants that naturally grow upon it. It is interesting to observe how close this relation in many cases is. 1. The sands of the sea-shore, and the margins of salt-lakes, are distinguished by their peculiar tribes of salt-loving plants;—the drifted sands more remote from the beach produce their own long waving coarser grass,—while further inland again, other vegetable races appear. 2. Peaty soils laid down to grass, or existing as natural meadows, produce one woolly soft grass almost exclusively (the _Holcus lanatus_); when limed, again, these same soils become propitious to green crops and produce much straw, but refuse to fill the ear. 3. On the margins of water-courses, in which silica abounds, the mare’s-tail (_Equisetum_) springs up in abundance; while, if the stream contain much carbonate of lime, the water-cress appears and lines its sides, and the bottom of its shallow bed, sometimes for many miles from its source. 4. The Cornish heath (_Erica vagans_) shews itself only above the serpentine rocks; the red clover and the vetch delight in the presence of gypsum; and white clover, of alkaline matter in the soil. 5. Then, again, plants seem to alternate with each other on the same soil. Burn down a forest of pines in Sweden, and one of birch takes its place _for a while_. The pines after a time again spring up and ultimately supersede the birch. The same takes place naturally. On the shores of the Rhine are seen ancient forests of oak from two to four centuries old,—gradually giving place to a natural growth of beech; and others where the pine is succeeding to both. In the Palatinate, the ancient oak woods are followed by natural pines; and in the Jura, the Tyrol, and Bohemia, the pine alternates with the beech. These and other similar differences depend upon the chemical constitution of the soil. The slug may live well, and therefore infest a field almost deficient in lime; the common land snail will abound at the roots of the hedges only where lime is plentiful, and can easily be obtained for the construction of its shell. So it is with plants. Each grows spontaneously where its wants can be most fully and most easily supplied. If they cannot move from place to place like the living animal, yet their seeds can lie dormant, until either the hand of man or the operation of natural causes produces such a change in the constitution of the soil as to fit it for ministering to their most important wants.