Some desert plants have large tap roots (tap root) capable of storing considerable quantities of water; one such root weighed 159lb.
This sometimes considerable growth and differentiation of the root is controlled by the activity of the root apical meristem, a region of meristematic tissue which is not terminal, but is covered by the tissue of the protective root cap. [...] Lateral roots (lateral root) are usually formed at some distance from the apical meristem.