'Eye' of potato is a type of :

Eye of the potato is the axillary bud. The axillary bud is an embryonic shoot which lies at the junction of the stem and petiole of a plant. As the apical meristem grows and forms leaves, it leaves behind a region of meristematic cells at the node between the stem and the leaf. These axillary buds are usually dormant, inhibited by auxin produced by the apical meristem, which is known as apical dominance. If the apical meristem was removed or has grown a sufficient distance away from an axillary bud, the axillary bud may become activated.