PERIODICITIES IN THE INFLUENCES OF AIR IONS ON THE GROWTH OF GARDEN CRESS, LEPIDIUM SATIVUM L.

When garden cress was exposed to either positive or negative air ions there was a net increase in the rate of growth, and an apparent periodicity, coincident with lunar phases, in the growth differences between the ion-treated and the control plants. A mechanism is suggested whereby lunar and other geophysical factors influence plant growth and other biotic phenomena.