AbstractRegions of different electron densities after concanavalin A‐peroxidase‐reaction have been observed in cell walls of intact cells as well as in isolated cell walls: In the peripheral region of intact cell walls two mannan layers appear. Treating isolated cell walls with pronase, NaOH, ethylendiamine or citrate buffer, respectively, we find con A binding spots in the inner cell wall regions which appear electrontransparent in the untreated cell walls. Apparently the mannan component of the inner cell wall regions is masked by proteins. In correspondence with chemical analysis our results cannot confirm the existence of inner cell wall regions which are free of man