Xylem is composed of four types of tissue

($i$) Tracheids Elongated or tube like cells with thick lignified walls and tapering ends. These are main water transporting elements

($ii$) Vessels A long cylindrical tube with lignified walls and large central cavity. It is a characteristic feature of angiosperms

($iii$) Xylem fibres have thickened walls and obliterated central lumen either septate or aseptate

($iv$) Xylem parenchyma is a thin cellulose and used to store food in the form of starch or fat