Unlike animals, not all regions of the plant are capable of division. Cells only divide in the meristematic regions like those at the tips of roots and shoots. Since the branch that I attached my swing to has already formed, it won't grown any higher. Just the tip of the plant will grow away from the branch. Growth in girth is caused by other meristems, called secondary meristems.
Secondary meristems develop after primary meristems.
The vascular cambium is a secondary meristem that divides to produce xylem and phloem cells. In trees like this one, it is the innermost layer of the bark Lateral roots, you know, come from another secondary meristem called the pericycle. It's found in the stele of the root. Who cares what that geek thinks.