SummaryAn account is given of the construction of tanks and chambers for the growing of plants under independently controlled soil and air conditions. The plants are grown in soil tins sunk in a water tank, the temperature of which is automatically controlled. Double‐walled glass chambers fit over the tanks, and within these the conditions of temperature and humidity are independently controlled. Artificial illumination is provided by two floodlights over each chamber, with 500‐watt gas‐filled lamps in each providing an illumination of the order of 1000 foot‐candles. The chambers were erected under a grant from the Empire Marketing Board for research on the bacterial disease of