540 .SOUTHERN FIELD CROPS 



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

 cotta or other suitable material for convejang the heat 

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

 be done should have numerous ventilators on two 

 sides. 



All curing learns are supplied ^^'ith 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. 

 17.5 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 dtiring the first few days after the plant is 

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

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

 be out 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° P.), by moderate moisture, and by dampness. It is 

 not customary to use artificial heat in yeUowing this tj-pe of 

 tobacco, especially with early-cut tobacco. . . . 



" The ne.xt change that takes place in the leaf is from the yellow 

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

 The first fires built under this tobacco should lie ^-ery small to 

 avoid danger of premature drj'ing of the tips of any of the lea^■es 

 not yet fuUj^ j'ellowed. The temperattire should not be raised 

 above 95° F. or 100° P. 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 well yellowed, to turn brown. A 

 few hours at this time will generally be sufficient. . . . This 

 process should be repeated every few days until all the gum 

 has disajipeared from tlie 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 tised 

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



