1. The amount of catalase in the dry seeds of rice is much less than that of wheat, barley, oats, and rye, being in fact about one-tenth as great. 2. Rice germinating aerobically contains much catalase, about seven-tenths as much as germinating wheat, barley, and oats. 3. The catalase does not increase in the course of anaerobic germination, but it does slowly in the course of germination in a medium which contains a reduced amount of oxygen. Hence the ratio of increase of catalase activity is a function of the free oxygen in the medium. 4. The free oxygen affects directly or indirectly the development of plumule and radicle, and also of the chlorophyll in it. 5. The catalase once increased by aerobic conditions decreases during anaerobiosis, while growth of the plant continues. 6. Aerobically grown seedlings with high catalase use much more oxygen than do anaerobically grown seedlings with low catalase activity. The anaerobic seedlings, however, give off a comparatively large amount of carbon dioxide during respiration, whether under normal aerobic or under anaerobic conditions.