Leaves from Zea mays grown in a dark room were exposed to the light from a 100 watt mazda bulb at a distance of 18 inches. At the end of 2 hrs. the leaves began to appear green and also the evolution of oxygen could be detected by use of luminous bacteria. This disagrees with previous findings that leaves of Vicia jaba and of barley had to be almost fully green before they began to carry on photosynthesis. No attempt was made to measure the CO2 exchange.