The composition of the cell wall of the stem and leaf sheath of extracted wheat straw was studied with Xray photoelectron spectroscopy and with a field emission scanning electron microscope equipped with an energy-dispersive microanalysis system. The outer side (epidermal side) had more lignin, and the inner side (lumen side) of the stem was rich in cellulose. The compositions of the two sides of the leaf sheath were a little different. The chemical components for the same tissue at different growth stages were essentially constant, and this indicated that cellulose, lignin, and hemicelluloses deposited in constant proportions in the cell wall of the same tissue during growth. (c) 2007 Wiley Periodicals, Inc.