Attempts were made to inject different substances into epidermal and stomatal cells in order to observe their movement from cell to cell and their effects on guard cell metabolism. Although injections of neutral red were successful and provided useful information, injections of ABA and KCl did not yield any worthwhile results. Measurements of pressure potentials in stomatal cells of four species were carried out. These throw light on the role of epidermal turgor in influencing stomatal movements and thus on hypotheses of a mechanical advantage of subsidiary cells.