Discs of cucumber leaves were kept at 2°C in the dark. When, subsequently, transferred to a temperature of 24 °C they develop symptoms of damage. The degree of injury depends on the length of the period at 2°C. An interruption of the treatment at 2°C by a short period at 24 °C reverses the damage induced by the cold treatment. The degree of reversal depends on the length of the cold period before the interruption and on the length of the interruption at 24 °C.