A series of experiments was carried out on the germination and growth of seed (cucumber) using a quartz Hg lamp and vitaglass, ordinary window glass, and ultra-glass (Corning 586 A W) as filters. Data with direct irradiation by the quartz Hg lamp and on controls (no irradiation) were also obtained. The results indicate that: shorter wavelengths in general appear to stimulate while the longer wavelengths inhibit germination; wavelengths of 320-390 m[mu] are particularly effective in inducing growth; wavelengths of 270-320 m[mu], appear to inhibit, delay the time, and lessen the rate of growth; and shorter wavelengths of light act as stimulating agents which modify the control of endogenous processes and accelerate germination.