Cells ‘left behind’ from shoot apical meristem, cannot modify into
Spine
During the formation of leaves and elongation of stems, some cells are left behind from the shoot apical meristem. These cells constitute axillary bud and are present in the axils of leaves and are capable of forming a branch or a flower. Axillary buds can modify into stem tendrils and thorns. Spines are modified from leaves or any part of a leaf.