Abstract In order to clarify the conditions necessary for obtaining maximum growth of plant cultures and maximum yields of active ingredients, a large cabinet was designed and constructed for growing cultures in a controlled environment. The cabinet, which is constructed entirely of wood, consists of two separate compartments, one above the other, each containing an illuminating system composed of a combination of fluorescent and incandescent lamps. A constant temperature is maintained in both compartments by a 1-horsepower air conditioner provided with coils for heating.