Uses of the Feulgen Reaction in Cytology. II. New Techniques and Special Applications

Procedures are described for use with the squash technique, whereby anthers, ovules, and root tips are fixed and stained in toto, then spread out into a layer one cell thick by squashing. 2. The smear squash method of studying chromosome structure, particularly the minor coil, is described. Contrary to most previous reports, the Feulgen stain was found to stain only the chromonema and not the matrix of the chromosome. 3. The Feulgen stain can be used with marked success after the trypsin-lanthanum digestive method of Caspersson, which removes the matrix of the chromosomes as well as other cell proteids. Preparations made in this way are particularly sharp and clear, and this method holds promise for the investigation of chromosome structure. 4. The anther squash technique is the first to reveal at all clearly the chiasmata and individuality of the chromosomes in forms that have a diffuse stage at diplotene and diakinesis. 5. Satellites can be revealed with remarkable clarity by the root tip squash method, and the anther smear squash method when used with pollen grains. A counter stain of fast green is used to differentiate the nucleolus.