The present experiments were perfortned to ascertain to what extent the temperature during colchicihe treatment affects the frequency of occurrence of polyploid plants. The materials used were radish (Raphanus sativus L.), buckwheat (Fagapyrulee esculetum MOENCH.) and adzuki bean (Phaseolus angularis W.F. WIGHT). The several kinds of colchidine treatment were ado.pted as follows t (1) soaking seeds in colchicine solution, (2) dropping colchicine solution on young buds, (3) dropping colchicine agar agar solution on young buds, (4) mounting colchicine lanoline emulsion to young buds, and (5) soaking seedlings in colchicine solution. Each treatment was carried out at lower (5-7'C) intermediate (15-20'C) and higher (25-30'C) temperature respectively, resulting in that the lower the temperature during colchicine treatment is, the higher the frequency of occurrence of polyploid plants, regardless of the kinds of colchicine treatment. This fact may be due to that, at lower temperature, the poisonous effect of colchicine. is almost negligible, but at higher temperature as soon as colchicine penetrates into cells and becomes effective for chromosome doubling, the cells begin to be killed from suffering the toxic action of colchicine, sa that, induction of 4x cells is hardly successful. The resistance to the toxic action of KCI03 showed that induced 4x radish is more susceptible to the toxicant th, an original 2x radish. It may be possible to use this test for distinguishing induced polyploid plants from original diploid ones.
