Abstract:The vessel element in the secondary xylem of Casuarina cunninghamiana was observed under an electron microscope. Three types of the vessel elements were found, a tail on each side, one tail only and no tail. Four types of perforation plates were present as follows： the scalariform perforation plate, the simple perforation plate, the scalariform-simple perforation plate, the simple and scalariform perforation plates symmetrically arranging on the same side of vessel, as well as some transitional types. The evolution of perforation plates in the vessel elements is discussed.