Resonance lysis of the cells in the leaves of the aquatic plant Elodea originally reported by Miller have thresholds at intensities of a few W/cm2. With pulsed ultrasound, the resonance behavior vanishes and the thresholds are at much higher amplitudes. This is similar to the characteristics of the thresholds for killing of Drosophila larvae by pulsed ultrasound. Both organisms contain small gas bodies within the tissues which may serve as nuclei for a cavitation related phenomenon. The results suggest that the response of these bubbles to continuous wave fields and very short pulses is qualitatively different.