Dry lettuce (Lactuca sativa L.) "seeds" (achenes) contain α-galactosidase (EC 3.2.122) at a level which is maintained in the imbibed dormant state in darkness. Both red light (R) and gibberellic acid promote an increase in enzyme activity several hours prior to the completion of germination. Germination and enzyme activity are not essentially linked, however, for the latter can increase while the former is inhibited. α-Galactosidase activity increases within the cotyledons and the endosperm following R stimulation, but the axis is essential to perceive the stimulus and to promote and maintain the increase in enzyme activity. A diffusible factor (or factors) is produced by and-or released from irradiated axes, and it migrates to the cotyledons (and possibly endosperm) to promote the increase in α-galactosidase activity. Gibberellic acid, particularly in the presence of benzyladenine, can replace the requirement for irradiated axes.