IO 



no sharp or unpleasant taste. In other words, it is 

 evident that marked chemical changes have occurred, 

 resulting in the destruction of substances which in burn- 

 ing give off undesirable compounds, and the formation 

 of other materials that give off in burning substances of 

 pleasant smell and taste. ( )n the other hand, if the leaf 

 be killed by chloroform or frost, the changes ordinarily 

 observed to result from curing do not occur. Curing is 

 parti v a life process, and is to some extent due to the 

 activity of the cells of the leaf. 



The Ripening of Tobacco 



Soon after the leaves of the tobacco plant reach 

 maturity, they undergo marked changes in colour and 

 other properties. The young growing leaf has an intense 

 green colour, shewing that it is quite rich in nitrogenous 

 constituents, which go to make up the living or vital part 

 of the leaf, and which are active in building up the food 

 supply of the plant. The object of topping (removal of 

 the flower head) and suckering (removal of the suckers 

 or offshoots) as practised by the tobacco-growers is that 

 the food built up by the leaves may accumulate in the 

 leaves themselves, instead of being carried away to the 

 seedhead and the offshoots. The result is that both the 

 size and thickness of the leaf are increased. The re- 

 served food supply of the mature leaf is deposited in the 

 leaf tissue in the form of starch granules, while the green 

 colouring matters arc dissolved and carried to the 

 vounger, growing parts. At this stage there is a 

 decided change in the colour of the leaf. Moreover, the 

 accumulation of the starch granules in the leaf causes 

 it to become brittle, so that it snaps when folded between 

 the fingers, ■■■ another characteristic sign of ripeness. 



