An inhibition of abscission in bean petiole explants is reported for additions of calcium salts, especially at concentrations between 10(-3) and 10(-1)m. Magnesium is less effective, and other commmon macronutrients are ineffective in inhibiting abscission. Evidence from timing experiments indicates that the calcium inhibition may act on the stage I or the "juvenile" stage of the explant, and that the inhibition of abscission may result from a retardation of senescence development in the pulvinar tissues of treated explants.