BONNER and DEVIRIAN (3) and BONNER (4) have shown that roots of different species vary appreciably as to the nutrients with which they must be'supplied for satisfactory growth in culture. ROBBINS (13) and WHALEY and LONG (15) have shown that roots of different lines of tomato differ particularly in vitamin requirements. The results do not make it clear as to whether the differences in response to added vitamins represent differences in ability of the roots 'to synthesize these substances for themselves or differences in ability to utilize the supplements. It can be anticipated, however, that if such differences exist among lines within a given species they may play some part in the development of general metabolic differences. It should be possible to study the inheritance patterns of these differences by utilization of root culture techniques in combination with a hybridization program to produce progeny in which these same characteristics can be investigated. The present study has been aimed at detecting the existence of line differences in roots of the tomato, Lycopersicon esculentum Mill. and related species with respect to the ability of the roots to synthesize and/or utilize thiamin, pyridoxine and niacin; at evaluating the significance of such differences; and ultimately at studying the inheritance of these differences.