The importance of the interaction between temperature and low-light intensity treatment in the de-vernalization of the Chrysanthemum has been confirmed. Low-intensity light caused no de-vernalization at or just above 180 °C., but at 23° C. 4 weeks of low light gave a considerable response, and at 28° C. it was practically complete. This effect of low-light intensity implicates carbohydrate supply as a possible factor in the de-vernalization reaction. The experiments described indicated, however, that lowering carbohydrate level by defoliation in full light did not cause de-vernalization, nor was complete darkness any more effective than dim light. Conversely, sugar feeding during low-light treatment failed to prevent devernalization. Stem elongation rates and leaf expansion rates confirmed that substantial amounts of sugar were in fact taken up, high rates being maintained in sugar-fed plants in contrast to the low rates of the water controls. Return to full light caused a rapid drop in stem elongation rates while increasing those of leaf expansion. Thus, while carbohydrate starvation may have a subsidiary effect, it would not appear to be the main factor involved in low-light intensity de-vernalization. Vernalization of etiolated plants and re-vernalization of de-vernalized plants also suggest that carbohydrate status is not the overriding factor in the vernalization reaction itself.