Root tips are fixed in aceto-alcohol (1 part glacial acetic acid, 2 parts absolute alcohol) for 24-48 hrs. Very thin slices of the tips are smeared on a slide and immediately flooded with aceto-carmin, followed by a cover glass. Using considerable pressure, the excess aceto-carmin is removed and the material flattened. Finally the slide is warmed to a point slightly below boiling. By sealing with gum mastic and paraffin, preparations can be kept 5-10 days.