The effect of sunlight on the growth of Pisum sativum etc. was studied under three different light intensities i.e. A. under diffuse light, B. under weak light (5% of A.) and C. in absolute darkness. The results were as follows: 1. The influences of illumination upon the germination of these plants: In the case of Pisum sativum the germination took place most rapidly when it was illuminated by weak (5% of A.) sunlight, while in the case of Allium ledebourianum it occured when the plant was exposed directly to the sunlight. The other plants remained indifferent to the light. 2. The development of leaves was usually proportional to the illumination; but in the case of Phleum pratense, L.? and Allium ledebourianum, the weaker the light intensity the more rapid was the rate of elongation of leaves. 3. The length of the stems influenced by the intensity and duration of illumination was as the follows: The length of the stems was in inverse proportion to the intensity of the illumination until the end of three weeks, and after seven weeks the plants which had been subjected to light of medium intensity had the longest stem of all; but after fourteen weeks the results were the reverse of those obtained by the short (3 weeks) illumination. 4. The number of internodes was not affected by illuminatoin, yet thier length was in inverse proportion to the intensity of the illumination during the initial period of growth. 5. Light had no effect on the length of the roots unless they were directly subject to illumination.