When barley seeds imbibe water, the O2 uptake of non-dormant seeds is considerably less than that of dormant seeds for at least the first 6 h, irrespective of the rate at which the seeds had previously lost dormancy. During the initial 6 h of imbibition, the CO2 output of dormant barley seeds is usually only slightly greater than and sometimes no different from that of nondormant seeds. The CO2 output of dormant seeds is reduced by about 66 percent by millimolar KCN, whereas that of non-dormant seeds is decreased by about 12–13 per cent only. The CO2 output of dormant barley in nitrogen is considerably less than the CO2 output of non-dormant seeds under the same conditions. Dormant rice seeds also show a higher initial O2 uptake than non-dormant seeds, though this is not generally as marked as in barley. Similarly, the initial CO2 output of dormant seeds is distinctly greater than that of non-dormant seeds, but in millimolar KCN it is depressed to a greater extent than in non-dormant seeds. In nitrogen, the CO2 outputs of dormant and non-dormant seeds were found to be the same. Consequently, unlike barley, dormant rice seeds appear to be as capable of carrying out alcoholic fermentation under anaerobic conditions as nondormant seeds. In barley, increasing the O2 tension from 21 per cent to 100 per cent increased the oxygen uptake of dormant seeds more than that of non-dormant seeds (an increase of 53 per cent as against 20–23 Per cent). In dormant seeds there was a concomitant increase in CO2 output (about 50 per cent), but the CO2 output of non-dormant seeds was hardly affected. High concentrations of CO2 are inhibitory to the germination of both dormant and non-dormant barley seeds. At a concentration of 10 per cent, however, CO2 is inhibitory only to dormant seeds, although at 2.5–5 per cent it is sometimes stimulatory to the germination of dormant seeds. A 24–h treatment with appropriate concentrations of ethanol, lactic acid, or acetaldehyde is also stimulatory to the germination of dormant barley seeds. Histochemical investigations in barley indicated the presence of peroxidase, cytochrome oxidase, and α-glycero-phosphate dehydrogenase in the embryo, aleurone layer, and in a layer associated with the testa. A number of other redox enzymes were detected in the embryo and aleurone layer only. No differences in distribution or intensity of activity were detected between dormant and nondormant seeds.