1. An extrusion phenomenon of the nuclear substance in Iris japonica is described. The figures of extrusion from one cell into the cytoplasm of adjacent cells are found in pollen mother-cells as well as in tapetal-, integumental-, nucellar-and ovarian cells. 2. The extrusion in the pollen mother-cells is observed to be most active in the synizetic stage and occurs not infrequently in the presynizetic, spireme and hollow-spireme stages and sometimes immediately before the diakinesis-stage. In somatic cells this process is generally found in the nuclei which are not in division. 3. The portions of the nucleus which are extruded may be chromatin, synizetic mass, spireme, nucleolus etc. 4. So far as the observation goes, I am inclined to side with the opinion that this phenomenon is chiefly caused by the fixing fluids and external injuries inflicted by pressure. It is with pleasure that I take this occasion to express my sincere thanks to Marquis YOSHICHIKA TOKUGAWA, the director of the TOKUGAWA Biological Institute, for all the facilities kindly offered throughout the course of this observation; my best thanks are also due to Professor FUJII of the Botanical Institute, Science College, Tokyo Imperial University for, his kind advice and valuable suggestion. I am much indebted to Viscount TADAMASA MIDUNO for his kindness in providing the materials used.