The interaction of auxins and diastase of malt was investigated in vitro, both in isolated and activated charcoal systems. Indole-3-propionic acid, indole-3-butyric acid, indole-3-acetic acid, and a-naphthalene acetic acid were used in concs. of 25 and 50 ppm. at 25[degree] C. In the activated charcoal systems 1 ml. of 1% diastase was adsorbed upon 1 gram of Norit A. The influence of the auxins on diastase, in isolated systems, was measured by determining the time required to digest a given amt. of soluble starch past the last iodine-staining stage. The influence of auxins on diastase in activated charcoal systems was measured by regular 1/2 hour comparative color tests with I2KI. Auxins retarded the action of isolated diastase and accelerated the action of diastase adsorbed on charcoal in the same order. The order of effectiveness from least active to most active was: indole-3-propionic acid, indole-3-butyric acid, indole-3-acetic acid, and a-naphthalene acetic acid. The effectiveness of the auxins was correlated with pH. It might be concluded hypothetically that there are two phases in the interaction of auxins on charcoal-adsorbed diastase: phase I, release of enzyme in whole or in part from the charcoal; and phase II, effect on enzyme action proper. If the influence of an auxin or factor dominates in phase I, then there is increased enzyme action and the factor can logically be called "growth-promoting." If the influence of the same auxin or factor dominates in phase II, then there is a decrease in enzyme action and the factor can just as logically be called "growth-inhibiting." The interaction of auxins and diastase on charcoal surfaces may well be the way in which auxins and enzymes interact on the surfaces of cellular colloids.