THE inhibition of the growth of lateral buds by the application of auxins in high concentrations to the apical surface of cut stems is well known, and it is often associated with marked swelling of the cut stems. Borgstrom1 explains both the inhibition and the swelling "as being due to increased supplies of auxin set free in a transverse flow from the phloem, induced by the decapitation of the main stem. He considers that the swelling is a secondary effect of the increased auxin supply and not otherwise related to the inhibition of the buds. In the experiments which are described below observations have been made on seedlings of Pisum sativum after treatment with H 11 extract of urine, three fractions of H 11 and some pure substances. The effect of the various applications on the growth of the cut epicotyls both in height and width and on the development and growth of lateral buds was examined. The plants were grown in pots of soil in the light until three or four internodes high, and then placed in the dark for twenty-four hours before experimenting and for forty-eight hours after treatment, being kept throughout the experiment under glass covers in a moist atmosphere. The inhibiting effect was calculated as the percentage difference between the averages for the total length of the side shoots in treated and control plants.