The inheritance of two characters in Manihot utilissima Pohl were studied. It was found that the leaves with narrow lobes V (Fig. 1) are dominant over leaves with large lobes v (Fig. 2) and that the brown coloration of the roots M (Fig. 5) is dominant over white m (Fig. 6). These two characters segregate independently, according to the dates recorded in tables III and IV. The phenotypic expression of the form of the leaves is largely dependent from the environment, the leaves with narrow lobes being replaced by leaves with large lobes in plants transported to a shady place under big trees. (Figs. 3 and 4). Thus reduction of light causes a change of dominance.