There is a difference between the stem of these two plants because Ranunculus is dicot and Zea mays is a monocot. Zea mays does not have a vascular cambium and has scattered vascular bundles composed of xylem and phloem tissue. On the other hand, Ranunculus has its vascular bundles in a ring arrangement and ground tissue is differentiated hypodermis, cortex, endodermis, pericycle and pith (there is no differentiation in Zea mays).