In the course of a series of investigations into the chemistry and physiology of foliage leaves, made some years ago by Messrs. Brown and Morris, among other discoveries of interest, those observers ascertained that the quantity of diastase that the leaves of many different species of plants can be shown to contain, varies considerably during a day of twenty-four hours. It is at its maximum in leaves gathered in the early morning, and at its minimum after a period of exposure to light, as in leaves gathered at 5 p. m. Those observers put forward two hypotheses to explain this phenomenon. The first is that during the day, particularly when the sun is shining, the diastase is used up gradually in dissolving a portion of the starch as it is formed in the chloroplasts, such portion being converted into sugar to meet the immediate needs of the cell protoplasm. This theory involves the acceptance of the view that the starch of the chloroplasts is the final product of the assimilation of the CO 2 absorbed and that its manufacture is altogether an “upgrade” process. Their experiments, however, led them to contest this assumption, and to put forward in contradistinction to it the theory that starch is, in the chloroplasts as elsewhere, always a reserve product, and that its appearance indicates that more carbohydrate is being formed than can be at once either used by the protoplasm or removed from the cell, the surplus being temporarily deposited by the protoplasm as starch. On this view the needs of the cell do not call for the conversion of starch into sugar, but are supplied from the sugar, which all botanists agree is antecedent to starch. They therefore reject this hypothesis, in the light of the experiments referred to, which are detailed in their memoir. Their second hypothesis, which they regard as a more probable one, is that the formation or secretion of diastase is irregular, being a starvation phenomenon, none of the enzyme being formed until the needs of the cell demand the transformation of the stored starch, either for immediate consumption in the cell, or for removal to a more permanent reservoir.