A study was made of the effect of seed vernalization and subsequent daylength on leaf number in vegetative plants of chicory and endive. In both species, vernalization and long day led to a marked decrease in number of leaves formed per unit of time. This corresponded with a decrease in fresh weight of the plant. The after-effects of low temperature on leaf morphology in chicory found by Hartman (1956) have been confirmed. In endive, vernalization leads to leaves that are longer, broader and thinner than those of unvernalized plants.