It was assumed in the previous paper that root hairs have better ability to oxidize the rhizosphere than that of other epidermal cells in rice roots. The present experiment was carried on to detect the oxidizing power of root hairs by observing oxidation of Fe⁺⁺ to Fe⁺⁺⁺ in agar culture containing ferrous sulfate. The following results were obtained. Two kinds of epidermal cells, i. e. haired short cells and hairless long cells, had the same oxdizing power in the region where the papillae first made their appearance in the epidermis about 5mm from the root tip. When root hairs elongated to more than 20μ in length, root hairs and hair-bearing cells had better ability to oxidize the rhizosphere as compared with hairless cells. Furthermore, the oxidizing power in fully-developed root hairs existed for long time, even after it was extinct in hair-bearing cells and hairless cells. These results were further ascertained by the distribution of peroxidase and hydrogen peroxide in the epidermis using the histochemical test.