In epiphytes (plants grow on another plant) the aerial roots are covered by a hygroscopic velamen tissue, which absorb moisture from the air. Xerophytcs are plants which grow on water deficient soil i.e., plants of dry habitat. They have well developed root system. Mcsophytes are such land plants which grow in moist habitats and need well-aerated soil. Root system is well developed, fairly branched with root cap and root hairs. The plants which grow in extremly wet soil or where water is available to plants in abundance are called hydrophytes. The roots are either absent (Wolffia, Salvinia) or poorly developed (Hydrilla).