The leaves of Cissus quadrangularis are normally seen growing near branch tips only, as they are short-lived. In this photo a couple of newly growing internodes or stem sections, with some leaves and tendrils growing at the nodes, i.e. where the sections link, can be observed.
Note how dramatically wavy the young ridges on the corners of the square stems are here on the new growth. On old stems these ridges are about straight, leathery and hard, almost cartilaginous. The leaves are petiolate, deeply lobed with three notable veins across their blades.