I. The P/O ratio, with succinate, of mitochondria from the cotyledons of peas was 1.0-1.5 during the first 2 days of germination; from the third day on it decreased till zero at the fifth day. 2. The uncoupling was caused by a mixture of long-chain fatty acids, which are formed during the homogenization of the tissue. 3. The uncoupling, therefore, is not due to changes in the mitochondria during germination.