CHEMICAL ANALYSES OF TOBACCO. 273 



In the foregoing experiment the retardation of the evaporation of the water from the leaves of the plant under 

 the bell jar was attended with a diminution in the absorption of mineral ingredients from thesoil. Thecarbo-hydrates 

 (in this instance starch), instead of undergoing transformation into other products, accumulated to an abnormal 

 extent. The consequence was precisely similar in character to that resulting from the deficiency of mineral 

 ingredients in the North Carolina tobacco (No. 10), only the accumulated carbo-hydrate in the last-named instance 

 was sugar, whereas in the former instance it was starch, the difference in this respect being probably attributable 

 to the difference in the other conditions of the experiment among which perhaps the most noteworthy in this 

 connection is the difference in the amount of albuminoids formed and in the percentage of sulphuric acid in the 

 plant. 



The differences in composition due to variations in the mode of cultivation are, apart from those arising from 

 differences in manuring, chiefly to be referred to the greater or less length of time that the plant is allowed to remain 

 in the field after it has been "topped". The operation of "topping", or removing the upper portion of the stalk, 

 is designed to stop the further growth of the plant and to direct the whole vegetative energy to storing the cells 

 already formed with the different organic substances, such as the organic acids, etc. The treatment of the seed- 

 leaf and the smoking tobaccos in this respect is notably different from that to which the tobaccos destined for chewing 

 are subjected. The former are allowed to remain on the stalk after "topping" until the expansion (i. e., cessation 

 of the growth of new cellular tissue, followed by " granulation ", that is to say, distension of the indi vidual cells from 

 accumulation of cell-contents) commences, say two or three weeks, while the heavier shipping leaf is allowed to 

 .stand until fully ripe, i. e., until the verge of decay is attained. During this period the increase in the cell-contents 

 is very marked to the eye, by reason of the greater thickness of the leaf as well as in the granulation of the surface 

 caused by the distension, of the iudividual cells. . 



The leaf being in both cases allowed to remain on the stalk until the expansion of the leaf, i. e., the formation 

 of new cellular tissue ceases, it is evident that the larger proportional amount of cellulose in the seed-leaf varieties 

 is due to a relatively more rapid production of ingredients other than cellulose in the other varieties during the 

 period of growth subseq uent to " topping" the plant. The smaller proportion of mineral ingredients, in spite of the fact 

 that the chewing tobaccos are usually produced on soil rich in mineral plant-food, and the disappearance of the nitric 

 acid, which is transformed into albuminoids and nicotine, would indicate that the removal of the " tops " has operated 

 to diminish the absorption at the roots. That the nitric acid in the tobacco plant has entered through the process 

 of absorption by the roots is clearly evident from the results obtained by Schloesiug, and previously cited, which 

 show that the nitric acid or nitrates are chiefly present in the midrib and in far smaller proportions in the substance 

 of the leaf. This distribution is entirely inconsistent with the theory of Nessler (op. oil., p. 28) that the nitric acid, 

 as well as the ammonia, has resulted from the fermentative alteration of the albuminoids. In treating of the 

 fermentation of tobacco it will be shown that while undoubtedly true of the ammonia, this theory is untenable in 

 regard to the nitric acid. Meanwhile it may be mentioned that Nessler (op. cit., p. 104) states that the total amount 

 of nitrogen in the plant is greatest at the time of its strongest (most rapid) vegetation, i. e., the middle of August, 

 diminishes gradually from that time until the beginning of September, and then appears to remain constant until the 

 point of absolute ripeness is attained or exceeded. The carbonate of potash in the ash increases until the middle 

 of August, the period of strongest vegetation, and after that diminishes regularly until after the point of ripeness 

 !s attained. 



CHANGES IN COMPOSITION OF TOBACCO INDUCED BY CUEING. 



According to the nature of the tobacco and the use to which it is to be applied, the operation of curing 

 consists either simply in expeditious drying, with such precautions as may insure a regular progress of the 

 operation and prevent the exudation of the juices which attends irregular and too rapid drying, or in drying 

 preceded by or accompanied with fermentation. 



As an instance of the first method may be mentioned the process of sun-curing, in which fermentation is 

 probably reduced to a minimum. In the case of the methods of slower curing by carefully regulated artificial heat, 

 a certain amount of fermentation probably takes place, although as shown by the large proportion of sugar 

 retained by some tobaccos cured by this method, the fermentation must in these cases have been exceedingly slight, 

 and probably restricted to those portions of the leaf that have been injured so as to expose the cell-con tents to 

 the air. The operation of slow curing by exposure to the air in barns or sheds is attended with a much greater 

 fermentative change, accompanied by gradual oxidation, while the process of " curing in its juices" to which 

 Perique tobacco is subjected represents a very thorough fermentation, with greatly reduced exposure to the air. 



In order to understand the changes produced by fermentation, it is necessary to consider in detail the 

 fermentative processes to which the different constituents of tobacco are liable. 



1. SUGAR. Of all the constituents of tobacco sugar is the most liable to change. As a rule the small 

 quantities found in the green leaf disappear completely during the process of air-curing, so that it is generally 

 stated that cured tobacco contains no sugar. While this is true of all of the air-cured samples analyzed, the 

 Kim cured (No. 3) and fire-cured (No. 5) contain notable proportions, while in the case of the North Carolina yellow 

 tobacco (No. 10), the carefully regulated drying by artificial heat has probably left almost the entire amount of 

 sugar unchanged in the leaf. 



867 



