The primary root is a downward prolongation of the primary axis of the plant.
In other cases the root structure of the stele continues up to the cotyledonary node, though the hypocotyl is still to be distinguished from the primary root by the character of its epidermis.
In many Dicotyledons and most Monocotyledons, the primary root soon perishes, and its place is taken by adventitious roots developed from the stem.
The growth of the primary root is limited; sooner or later adventitious roots develop from the axis above the radicle which they ultimately exceed in growth.
The half of the embryo directed towards the archegonial neck gives rise to the apex of the stem and a sheath of three leaves, the, other half to the small foot and the primary root.
