Further studies on the binding of pectin methylesterase (PME) to cell wall preparations are described. The PME of extracts of wall preparations from artichoke tubers was separated into three fractions, A, B, and O. Two similar fractions (A and 0) were obtained from tobacco pith wall preparations. The amount of fraction A type PME which could be adsorbed to wall preparations was increased by the addition of 2,4.dichlorophenoxyacetic acid (2,4.D), but not by calcium ions. Neither 2,4.D nor calcium increased the adsorption of fraction B, but calcium and not 2,4�D increased the amount of fraction 0 adsorbed to the wall preparations.