STUDIES ON THE CUEING OP LEAF TOBACCO. 31 



of weight in curing between leaves harvested on the stalk and those 

 picked from the stalk may be much greater with some of our manu- 

 facturing and export types, which are grown under different con- 

 ditions and harvested in a much riper state than the cigar-wrapper 

 types. It will be seen that in stalk curing there was a loss of about 9 

 to 10 per cent of the original content of pure ash, which is in close 

 agreement with Mohr's results. In curing the primed leaves there 

 can, of course, be no loss of ash. Our results show that, although 

 the cured picked leaves contain little or no starch, the removal of 

 insoluble carbohydrates is pushed considerably farther when the 

 leaves are cured on the stalk. There is a more marked decrease of 

 pentosans in stalk curing. There is no essential difference in the 

 results as between the two methods with reference to sugar content, 

 since in both cases there is a practically entire disappearance of 

 sugars when the curing is complete. 



The compounds of nitrogen are decidedly the most important con- 

 stituents of the leaf in regard to differences in the results of curing 

 on the stalk as compared with curing the picked leaves. For the 

 three years for which direct comparisons are made, the loss in protein 

 nitrogen in the leaf web, and particularly in the midrib, was decidedly 

 greater in stalk curing than in curing the picked leaves. Since the 

 temperature employed in drying the samples was sufficient to expel 

 the easily volatilized portion of the nicotine, no definite conclusion 

 can be drawn as to the differences in loss of this constituent in the 

 two methods of harvesting. The results regarding nitrate nitrogen 

 are unsatisfactory, doubtless because of the difficulty in obtaining 

 reliable results with the uncured material, as pointed out on page 28. 

 As a whole, the results do not indicate a very marked translocation 

 of nitrates into the stalk. As far as they were carried, our results 

 indicate that ammonia is readily translocated into the stalk. 



In comparing the results of the two methods of curing with refer- 

 ence to changes of composition, the most striking difference is to be 

 found in the behavior of the nitrogenous cleavage products from the 

 hydrolysis of protein. From 40 to 60 per cent of the protein is 

 broken up during the curing process and, although the loss in total 

 nitrogen in curing the picked leaves shows conclusively that a por- 

 tion of the nitrogen of the decomposition products escapes as ammo- 

 nia, the loss thus involved is but a comparatively small portion of 

 the whole. The result is that there is a marked accumulation of 

 amid and amido compounds in the cured picked leaves, the increase 

 in this form of nitrogen amounting to 0.5 to 1.5 per cent of the leaf 

 weight, or 100 to 400 per cent more than was contained in the uncured 

 leaf. In the stalk-cured leaves, on the other hand, not only are the 

 products resulting from the splitting of the protein completely 

 removed, but a considerable portion of the amid and amido com- 



