1100. Mixed or secondary soils include not only primitive earths, or the debris of rocks, but vegetable matters-not only the medium through which perfect plants obtain their food, but that food itself. In this view of the subject the term soil is used in a very extensive acceptation, as signifying, not only the various sorts of earth which constitute the surface of the globe, but every substance whatever on which plants are found to vegetate, or from which they derive their nourishment. The obvious division of soils in this acceptation of the term is that of aquatic, terrestrial, and vegetable soils ; corresponding to the division of aquatic, terrestrial, and parasitical plants.
