changes in composition, the green colour is replaced by a 

 lemon yellow. This change from green to yellow takes 

 place in all tobacco whatever the method of curing may 

 be, if it is properly conducted. The green colouring 

 matter or chlorophyl of the tobacco leaf, is found in all 

 green plants in very similar, but not identical forms. 

 During the period in which the leaf issue is undergoing 

 starvation, the green colouring matter is more or less 

 completely changed into colourless substances ; and the 

 appearance of the yellow colour marks the approaching 

 death of the leaf. It must not be thought that the yellow 

 colouring matter is formed during the curing process, 

 directly from the green colouring material. - The yellow 

 colouring matter is contained in the green leaf before it 

 is harvested, and also after it has turned brown. The 

 yellow is simply obscured in these cases by the more 

 intense green or brown. 



In building a good barn for the air-curing of tobacco, 

 the two principal considerations to be kept in mind are to 

 construct it as nearly air-tight as possible, and at the 

 same time to provide an efficient system of ventilation ; 

 for in the absence of any method of supplying artificial 

 heat, these constitute the only means of controlling cur- 

 ing conditions. The fundamental principle to be kept in 

 mind during the first stage of the curing is to avoid too 

 rapid drying out of the leaf. Many growers, in their 

 anxiety to avoid damage from pole-sweat, caused by ex- 

 cessive moisture, injure their tobacco very seriously In- 

 going to the other extreme of drying out the leaf so rapid- 

 ly as not to allow sufficient time for the changes to take 

 place, which arc essential to good curing, dependent on 

 the life activities of the leaf, and are, therefore, stopped 

 as soon as this is killed hv loss of w ater Consequently, 



