The effect of various wavebands of visible radiation, used to lengthen short daylight periods, on the photoperiodic response of plants has been the subject of considerable disagreement. Schappelle (9) concludes that supplemental red and blue radiation are equally effective in inducing flowering in radish and spinach, that red is more effective than blue in the case of China aster and early flowering cosmos and that blue is more effective than red in the case of lettuce, although red induces flowering. Salvia, chrysanthemum, Kalanchoe, teosinte, and Maryland Broadleaf tobacco failed to flower under any radiation prolonging the daylength to more than ten hours. Funke (3, 4, 5) divided his results into four types of flowering response when he supplemented an 8-hour day with red, blue, and white radiations. Group I included those plants which flowered under short days and blue at the same time and under white and red at the same time ; plants of group II failed to flower under short days but flowered under all long day conditions ; those in group III flowered only under white radiation and under no other condition ; and those in group IV flowered simultaneously under white and blue radiation and under red and dark at the same time. He used a light intensity of from 30 to 60 lux (approximately 3 to 6 foot candles) and a temperature of 12? to 15? C. Rasumov (8) found that, in general, red light acted like white light in inducing flowering in long day plants and inhibiting flowering in short day plants ; green, blue, and violet light acted like darkness. He found, however, a variable sensitivity to differences in wavelengths of radiation. Withrow and Benedict (11), and Withrow and Blebel (12) found that red and white radiation induced early flowering in long day plants and inhibited flowering in short day plants. Short day plants flowered in days lengthened with green and blue light, as well as under short days. Some long day plants, such as China aster and Helianthus cucumerifolius also flowered under blue radiation at the same time as under the red, while Scabiosa, another long day plant, failed to flower under the blue. The plants were grown at 50? F. night and 55? F. day temperature.