Their structure can be discerned best in a cross-section through neighbouring cells. The middle lamina between the cells is preserved within the pits. Their centre is made up by a disc of primary cell wall material, called torus . No secondary walls exists in the pit's structure. Bordered pits exist only in cells with secondary walls.
Wood vessels are the chief water-conducting elements of angiosperms.
In contrast to the tracheids are the final walls of the single vessels perforated or, much more so, completely resolved. Wood vessels are therefore generally thought to be more efficient water conductors than tracheids. It can be as long as several meters. It is commonly assumed that the wood vessels are at least in some species as long as the whole shoot. During ontogenesis are the wood vessels strongly widened.