7. A method has been developed for studying mitoses in developing endosperms particularly to correlate types of figures observed with the occurrence of endosperm and aleurone mosaics. Collections made six days after pollination usually had many divisions. Material was fixed according to Randolph's chromo-acetic formula (Randolph, L. F.  J. Agr. Res, 53:881-916). Whole mounts or free hand sections were stained by the usual Feulgen method with the omission of destaining or washing off excess fuchsin in SO₂ water (by putting the tissue from the fuchsin-sulphurous acid directly to water and, as the nuclei become stained, changing the water several times before the usual dehydrating and mounting). Preliminary observations show 4-10 percent abnormal divisions in endosperms collected from stocks giving high rates of mosaic formation.