304 EXPERIMENT STATION RECORD. 



ventilator; in the last a lighted lamp could be placed to assist in 

 the ventilation. The results of curing tobacco hung in this building 

 are tabulated. 



The loss of water in curing was about 71 per cent of the weight of 

 the green i)lant. 



To investigate the conditions afi'ecting the escape of water from the 

 leaves, circular disks were cut between the veins in different stages of 

 the curing, weighed, exposed for a given length of time to the air in 

 an air-tight space, and again weighed. From 5 duplicate trials it 

 appeared tliat the period of most rapid escape of water was when the 

 color was changing from yellow to brown. The changes in color were 

 not directly due to loss of moisture, the particular shade of brown 

 depending largely upon the degree of ripeness. 



An attemjit was made to determine the highest degree of atmos- 

 pheric moisture possible during the curing process without incurring an 

 attack of pole burn, by employing a curing chamber in which the tem- 

 perature and moisture could be controlled and kept uniform. 



The chamber and the psychrometer used are described, and the 

 results obtained in the curing tests are shown graphically. 



The author says: "From these data the conclusion seems warrant- 

 able that with a temperature within the curing house of not exceeding 

 75° F., a degree of atmospheric humidity represented by a wet bulb 

 depression of 2°, when the psychrometer is between the plants, and is 

 not subject to unusual air currents, does not expose the tobacco to 

 pole burn, and that an occasional variation to 1° is safe, at least if not 

 prolonged. But a wet bulb depression of less than 1° is dangerous, 

 and if prolonged is almost sure to result in jjole burn." The water 

 appears to be set free by the leaves rather than to be extracted from 

 them by drying. 



Pole burn is the decay of the leaf resulting from a too ])rolonged 

 exposure to the excess of water within the substance of the leaf It 

 can be prevented by sufticient ventilation of the curing house. 



Ventilation of the curing house (pp. 3(15-370). — A 6-inch hot-air flue 

 placed a short distance above the floor was used, starting from a small 

 stove at one side of the building, below the sill, and emerging on the 

 same side a short distance above the sill, after traversing all the com- 

 partments. With this the humidity of the air was easily regulated. 

 Four 3(j-inch box stoves, carrying 7-inch pipe, would be sufficient for a 

 curing liouse 100 ft. long; the pipe should have an ascent of 10 in. to 

 the rod. 



Laths 4 or 5 in. apart and containing G medium plants are rec- 

 ommended. 



"In curing tobacco the aim should be to have it cure in as moist an 

 atmosphere as possible without incurring damage from pole burn." 



Wheat, W. C. Latta {Indiana 8ta. Rpt. 1895, pp. 35, 37, ^0).— This 

 is a continuation of work published in Bulletin 50 of the station 



