Summary:
AT the red edge of the invisible in the spectrum there is a narrow band of light waves which have a powerful and hitherto unsuspected biological inhibitory effect. This is reported by Lewis H. Flint, of the Department of Agriculture, and E. D. McAlister, of the Smithsonian Institution (Smithsonian Misc. Coll., 94, No. 5, June 24, 1935), as a result of further studies of the germination of dormant lettuce seeds when exposed to radiation.