Plant structural component of the plant. Chlorophyll, a green-colored, magnesium-containing pigment is essential to this process; it is generally present in plant leaves, and often in other plant parts as well. Parasitic plants, on the other hand, use the resources of their host to provide the materials needed for metabolism and growth. Plants usually rely on soil primarily for support and water (in quantitative terms), but they also obtain compounds of nitrogen, phosphorus, potassium, magnesium and other elemental nutrients from the soil. Epiphytic and lithophytic plants depend on air and nearby debris for nutrients, and carnivorous plants supplement their nutrient requirements,
Jethro Tull (agriculturist) the plant." Again, he declares elsewhere, "That which nourishes and augments a plant is the true food of it. Every plant is earth, and the growth and true increase of a plant is the addition of more earth." And in his chapter on the "Pasture of Plants", Tull told his readers with great gravity that "this pasturage is the inner or internal superficies of the earth; or, which is the same thing, it is the superficies of the pores, cavities, or interstices of the divided parts of the earth, which are of two sorts, natural and artificial. The mouths or