THE TOBACCO PLANT. 43 



the production of seed, the root retains only a small 

 residue of these constituents, and the soil is correspond- 

 ingly exhausted of them. 



As it is with the turnip, so is it with culmiferous 

 plants. If they are cut off before flowering, a consider- 

 able portion of the nutritive substances stored up in 

 them remains in the root, which the soil of course loses, 

 if the overground plant is removed after the ripening 

 of the seed. 



The experience derived from the cultivation of 

 tobacco gives a clear view of the processes in the devel- 

 opement of an annual leafy plant. 



In the tobacco plant the overground and the under- 

 ground parts grow with perfect equality ; the root gains 

 in extent, in the same proportion as the stem lengthens 

 and the leaves increase in number and size. There is 

 no appearance of sudden changes in the direction of or- 

 ganic activity, no shooting, but the phases of life in the 

 plant follow in steady continuous progression. Even 

 while the top of the stem bears ripe seeds, and the 

 lower leaves have withered, the side shoots of the plant 

 are often still putting forth flower-buds, the seeds of 

 which will ripen at a much later period. 



The tobacco plant is remarkable for producing in its 

 organism two nitrogenous compounds, of which the one, 

 nicotine, contains neither sulphur nor oxygen ; while 

 the other, albumen, is identical with the sulphureous 

 and oxygenised constituents of the cereals and other 

 alimentary plants. 



The commercial value of tobacco leaves is in an in- 

 verse ratio to the amount of albumen which they con- 

 tain, that sort of tobacco being most highly esteemed 

 by smokers which contains the least albumen ; for the 

 latter ingredient, in the burning of the dry leaves, emits 

 on carbonisation a most disagreeable smell of burnt 

 horn shavings. The leaves rich in albumen contain, as 

 a rule, more nicotine than those which are poor in albu- 

 men ; they give the strongest kinds of tobacco, many of 

 which cannot be smoked unmixed. 



The tobacco leaves cultivated in France and Ger- 



