Control of soil temperature is required in many biological studies involving growing plants or organisms associated with them. Controlled environment cabinets can be used but are expensive and therefore simpler, inexpensive alternatives have been designed. The Cornell Temperature Tanks (Ferris et aI., 1955) use converted milk coolers to cool water in which glazed pots, containing soil and plants, are immersed. Several other variations of water baths have been described (Kijne and Jacob, 1963; Harrison et aI., 1965; Steele, 1967). Although a water medium allows control of temperature within well defined limits, the use of circulating air is generally simpler and provides more flexible usage. Earley and Cartter (1945) designed a box structure incorporating a thermostatically controlled air-heating and cooling system in which were placed solution bottles and gravel culture jars containing the soybean plants they were studying. Fassuliotis (1962) used a converted soft drink dispensing machine to provide the cooling unit in a simple box in which air circulated around suspended plant pots. Lownsbery and Mitchell (1965) used a similar system but with a domestic air conditioner to provide cooled air. Controlled temperature cabinets designed and constructed at the Scottish Horticultural Research Institute recirculate cooled or heated air within the body of the cabinet; a flexible arrangement of top covers allows a variety of different size soil containers to be used. The following description refers to stock commercial items from which the cabinet were constructed; the s ize can be varied but must be re lated to the capacity of the refrigeration compressor.
