When the retort is filled with aromatic plants and steam is admitted through the pipe from the boiler, the volatile oil is extracted in the form of a vapor, which is carried over with the steam to the condenser, where both are condensed to liquid form. The oil and water together flow from the condenser into the receiver, one type of which is constructed like an ordinary milk can and is fitted with a siphon leading from the bottom, through which the water is drawn off to prevent the receiver from overflowing. Many volatile oils will float on the water and may be drawn off from the top of the receiver at will. Other oils, such as sassafras and wintergreen, are heavier than water, and should be collected in a receiver provided at the bottom with an outlet tap through which the oil may be drawn off. The cost of setting up a still will depend upon what facilities are already at hand and upon the size and efficiency of the apparatus installed. It may easily range from a small sum to several thousand dollars. YIELD. The yield that can be obtained from drug plants in different localities will naturally vary according to the suitability of the situation for the plants selected for cultivation. Even in the same locality wide variations in yield will result from differences in the lay of the land and in soil, drainage, and seasonal conditions. The skill of the grower and the degree of care and attention which he bestows upon his crop are also factors affecting yield. Many of the drug plants mentioned in this bulletin have not been grown on a scale large enough to give a very satisfactory basis for calculating yields. Acreage yields calculated from the product of small garden plats are generally untrustworthy, since in such plats the plants are usually more favorably situated with respect to soil and are given better culture than when under field conditions. Moreover, as the area increases, it becomes more difficult to maintain an approximately perfect stand and to protect the crop from the ravages of insects or other destructive agencies. The returns from small experimental areas can at most be regarded as only an indication of the yield that may be expected under favorable conditions, and the prospective grower will do well to proceed cautiously until he has determined for himself the possibilities of yield in his particular location. MARKETING.