A Section-Smear Method for Plant Cytology

An improved method for making root tip preparations of plants with medium or small chromosomes is described. Division figures are oriented in polar view by cutting paraffin cross sections of roots; the pectic substance is removed from the middle lamellae and the sections then are smeared. The procedure recommended is as follows: Kill root tips in Navashin or other fluid containing chromic acid. Wash, dehydrate, embed in paraffin, and section transversely. Stain slides bearing the sections by a Feulgen technic following the modification of De Tomasi, except that the hydrolysis is prolonged to 45 minutes, and a 10-minute washing in running water is introduced between the fuchsia and the first bath in sulfite solution. Dehydrate and mount in thin Canada balsam; then apply local pressure to top of cover glass with the tip of a scalpel, while observing the action under low power of a microscope. The prolonged hydrolysis softens the tissue and removes sufficient pectic substance so that cells of the section sep...