SUMMARYExperiments on leaves of tomato, sugar beet and cocksfoot show that uptake of diquat and paraquat, although rapid in the light, is increased by darkness and therefore takes place through the cuticle and not through stomata. Darkness for as little as 4 hr. increased uptake almost twofold.Diquat and paraquat are rapidly and strongly adsorbed both to leaf tissue and to extraneous matter on the leaf surface.Uptake in the field is so rapid that rain immediately after treatment has little adverse effect.