540 SOUTHERN FIELD CROPS 



tilators in the top, with a furnace, and with flues of terra- 

 cotta or other suitable material for conveying the heat 

 through the barn. Structures in which air-curing is to 

 be done should have numerous ventilators on two 

 sides. 



All curing barns are supplied with the necessary in- 

 terior framing to support the sticks on which the tobacco 

 is hung. 



Fire-curing. — The method practiced in the dark-tobacco dis- 

 trict of south-central Virginia is thus described in Bulletin No. 

 175 of the Virginia Experiment Station : — 



" The yellowing stage is the first step in the curing process. 

 The change to yellow is caused by a breaking down of the green 

 chlorophyll granules during the first few days after the plant is 

 cut. The riper the tobacco, the more quickly will this change 

 take place. Therefore, to yellow uniformly, the plants should 

 be cut as nearly as possible at a uniform stage of ripeness. This 

 change in the leaf is favored and hastened by a gentle warmth 

 (about 90° F.), by moderate moisture, and by dampness. It is 

 not customary to use artificial heat in yeUowing this type of 

 tobacco, especiaUy with early-cut tobacco. 



" The next change that takes place in the leaf is from the yeUow 

 to the brown stage, and for this purpose artificial heat is used. . . 

 The first fires buUt under this tobacco should be very smaU to 

 avoid danger of premature drying of the tips of any of the leaves 

 not yet fuUy yellowed. The temperature should not be raised 

 above 95° F. or 100° F. at this first firing, and should be main- 

 tained only long enough to dry out the surface moisture and start 

 the tips of the leaves, already weU yeUowed, to turn brown. A 

 few hours at this time will generaUy be suf3.cient. . . . This 

 process should be repeated every few days until all the gum 

 has disappeared from the leaf and the tips of the leaves have 

 begun to take on the brown color. After these conditions have 

 been attained, a somewhat higher temperature may be used 

 safely if the moisture supply is sufficient not to result in the dry- 



