Since the author (1929) found that the resistance of the toxic action of KClO3 correlated positively with the drought resitance in seedlings of rice varieties, the close relationships of the toxicant resistance to the other several kinds of characteristics of certain plants have feen observed by him as well as others, the results hitherto obtained being briefly summarized as follows. (1) Cold resistance: The cold resistant varieties are less resistant to the toxicant (Wheat, Barley, Rape, Genge, Radish, Brassica, Loquat and pine trees.) (2) Drought resistance: The drought resistant varieties are more resistant to the toxicant (Rice-Paddy and Upland rice-Upland rice only.) (3) Earliness in ripening: The earlier varieties are less resistant to the-toxicant than the later ones (Rice and Sugar-cane) (4) Sex: (a) The males are more resistant than the females (Hemp, Spinach Aucula Japonica and Remux Acetosa L.) (b) The males are less resistant than the females. (Papaya, Strawberry and Asparagus) (5) Double flowered and single flowered plants: Double flowered plants are more resistant than the single flowered ones. (Matthila incana and other many kinds of flower plants) (5) Virus diseased plants: Diseased plants are less resistant than healthy ones (Many kinds of vegetable crops and Tobacco plant.) (7) F1 plants: F1 plants are more resistant than either of their parents (Egg-plant) (8) Teratological forms: Teratological forms, especially in sexual organs, are more resistant than the normal ones (Rice) showing the materials used in the auther's experiments. Basing on the results of various kinds of tests with rice and wheat plants, the auther has ever put forward the hypothesis pertaining to the physiological cause of the toxicant resistace as is shown below: The chlorate itself is practically harmless to plants, but the salts are reduced by the reducing substances contained in plants, such as glucose, aldehydes, etc., resulting in the formation of hypochlorite which acts directly poisenous on plants and consequently the resistance to the toxicant is dependent on the amount of the substances concerned, i. e., the more the amount of the latter, the less the resistance to the toxicant. (Here, the amount of the reducing mattersiod in plants was compared by that of the ine consumed by the oxidation.) By the further study, the above-noted hypothesis is found also applicable in the case of the toxicant resistance with thesex es as well as double versus single flowering. The reducing substances, it may be believed, have much to do with the problem of the oxidation-reduction within plants. This idea is supported by estimating the activity of catalase (oxidizing agent) and the amount of the ascorbic acid (reducing agent) with rice, wheat and flower plants. From the results of the present research, it may be noticed of most importance to find out the reason why the characteristics conserned have the certain relationships with the oxidation-reduction reaction within plants for which some study along this line is now under way in the author's laboratory.