2. A method for making smears of root tip chromosomes. Frequently it is necessary to have counts of root tip chromosomes, but the paraffin method for making preparations is laborious and time consuming. However, excellent figures can be obtained quickly and easily by the following technique. Fix young root tips in Carnoy's fluid for 6-24 hours. Change to 70% alcohol. (The material can be kept here until it is convenient to make the smears). Transfer to equal parts of hydrochloric acid and 95% alcohol for five minutes, then to 70% alcohol for at least five minutes. Put a thin cross-section slice of the root tip into a drop of aceto-carmine on a slide, and tease the material apart with needles, or flatten it with a scalpel. Put on a clean cover glass and press gently with the eraser end of a pencil. Heat slide several times by passing through a flame. Examine to see whether there are sufficient division figures. If not, make a smear from a different section of the root, or from a different root. A good preparation has the cells well separated but intact, with many well-stained division figures. Temporary mounts can be sealed with a gum-mastic-paraffin mixture and kept in a cool place for several weeks. Or the slides may be made permanent by McClintock's method for making sporocyte smears permanent.