1. Difference in the amount of 1332 absorbed by the leaf (of several kinds of plants), floated on the surface of the solution or immersed in the solution, was measured under the condition of the diffused light or in the darkness. 2. Generally speaking, the amount of P32 absorbed in the ligh t condition was larger than that in the dark. 3. The value of the ratio of the quantity of the radioactive substance absorbed in the dark to that in the light was relatively small when the substance was imbibed through the upper surface (mainly through the cuticle) of the leaf; and the value of the ratio standed more closer to 1 when the absorption was erformed through the lower surface (through the cuticle and stomates) of the leaf. 4. If the wetting agent was added to the solution, the absorption through the lower surface of the leaf was larger in the dark than in the light. 5. When the leaves were immersed in the solution, the absorbed P32 in the dark was lesser than that in the light ; nevertheless the amount of absorbed water in the dark was larger than that in the light. 6. From the results of these experiments the a uthors came to the conception that there were two factors in relation to the absorption of P32 : namely (a) the metabolic activity in the cell operating as the generative cause of the absorption and (b) the physical mechanism of the outer cover of the plant. Concerning the factor a it was ascertained without difficulty that the light accelerated the absorption ; as to factor b the cuticle permitted the manifestation of the function of a rather plainly, but the stomate did not always allow to express exactly the result of a, and inversely the latter hindered the absorption greatly in the light, under certain conditions, because of the presence of 02-bubbles evolved by the carbon assimilation.