Plants must provide thirsty leaves with an ample supply of water and minerals on a continual diurnal basis otherwise leaves wilt and the plant will die. With some trees that span heights of 100 meters, overcoming the forces of gravity and the resistance to drag, make this process a very impressive feat. Because nature always finds the cheapest way to do work the entire process requires no input of internal energy from the plant (except for the building cost of the hydraulic path itself). The hydraulic path (xylem) is composed of living and dead cells. It is the dead cells that serve as the hollow water conducting pipes. These pipes (or stacks of these pipes) are separated by primary cell wall material which turns out to serve many significant evolutionary features that enable plants to overcome the forces of gravity and friction while either avoiding, tolerating or refilling embolism when and/or if they form.