Xerophytes are defined as plants of dry habitats. Leaves of xerophytes are much reduced, scale-like bearing stomata of sunken type confined only to lower epidermis. In some xerophytes-like Nerium, stomata are situated in pits lined with hairs. Hydrophytes grow on extremely wet soil where water is available to plants in abundance. Stomata are completely absent in submerged leaves, present only to upper surface in floating leaves and on both the surface in emergent forms. Mesophytes are such land plants which grow in moist habitats and need well-aerated soil, stomata generally present on both the surface of leaf. Heliophytes grow best in full sun-light.