When lignin is extracted from cornstalks by a large excess of lactic acid two major changes occur, namely a rapid initial process and a slow time-determining first order reaction. The temperature coefficient of the slow part of the reaction is negligible;A hydrolytic effect appears to play an important role in the extraction of lignin from plant tissue by both alcohols and organic acids;Evidence indicating that aqueous solutions of formic acid containing hydrochloric acid may cause lignin in plant tissue to undergo condensation-polymerization reactions is presented;Fractionation takes place when lignin is extracted from plant tissue by organic acids;Anhydrous organic acids form esters with the lignin that they extract. Esterification plays no important role in the extraction of lignin from plant tissue by aqueous solutions of organic acids;In most cases the action of organic acids on isolated (caustic alkali) lignin is not the same as their action on natural lignin;Lactic acid adds free carboxyl groups to both natural and isolated lignin. It is possible that this acid combines with lignin according to the mechanism Holmberg (43) proposed to explain the action between alcohols and lignin;Isolated cornstalk lignin does not give a color change when treated with Wiesner's reagent.