TOBACCO. 199 



and finish of the leaf. If the leaves are harvested 

 too green, the colour will be dull and dark, because 

 they contain too much chlorophyll, and if harvested too 

 late (ripe), the colour v^all be uneven, mottled, and lacking 

 in freshness, because they contain too little chlorophyll. For 

 these reasons too-green leaves when cured are tough and 

 leathery, and over-ripe leaves, strawy and lifeless to the 

 touch."" 



A number of changes were formerly attributed to bacterial 

 action, but this theory has now been disproved, and the view is 

 held that Che majority of these changes are due to enzymes, 

 the actions of which have been, in many cases, correlated with 

 definite changes. 



" When the plant is slowly starving to death, as it is when 

 it is cut and allowed slowly to dry, there is a rapid formation 

 of these enzymes, which separate themselves from the proto- 

 jilasm and push out through the plant in search of food for the 

 dying plant cells. Having thus distributed themselves, the 

 enzymes are in position to become soluble again, and take up 

 the work of fermentation whenever the conditions become fav- 

 ourable, as they do in the fermentation pile. If the leaf be 

 killed outright by heat or rapid drying, the enzymes will have 

 no opportunity to escape frorn the protoplasm, but will become 

 entangled with the insoluble protein, so that later, when the 

 leaf is brought into condition for fermentation, the process will 

 be a total or partial failure, since these enzymes are active only 

 when in solution. 



"To repeat, the chemical changes which develop the aroma, 

 as well as eliminate undesirable products, are due to certain 

 enzymes. These changes take place during the second stage 

 of the curing process, which is called the fermentation, or 

 ' sweat.' But these enzymes are largely developed in the 

 first stage of curing, and unless the first stage is properly con- 

 ducted, the enzymes will not exist in larce quantities, or in 

 available forms, and the products developed during fermenta- 

 tion will be disappointing."® 



Development of the Bkown Colour. — " The slow star- 

 vation process of the tobacco leaf in the curing barn is con- 

 nected with the yellowing of the leaves, followed by the 

 characteristic brown. The yellow^ colour is chiefly due to the 

 etiolating of the chlorophyll granules because of the absence 

 of bright daylight, and sets in while the cells are still alive, 

 while the brown colour sets in after their death. The changes 



