alg 
by the mosaic disease contains much less soluble albumin than normal 
leaves, for an equal surface. The latter give a juice which, upon being 
heated, forms a large amount of flocculent coagulum; the former, how- 
ever, hardly more than a turbidity. This is not surprising, since the 
chlorophyll bodies are affected in the mosaic disease and hence can not 
furnish a sufficient amount of sugar for an abundant protein formation. 
The fat content varies considerably, the amount being—other things 
being equal—probably influenced by the weather, since low tempera- 
ture will retard growth and respiration more than it does assimilation; 
hence some sugar that would otherwise have been consumed by respi- 
ration may be transformed into fat, if the conditions for protein forma- 
tion are not all fuifilled at that time. The sugar is the material from 
which not only the cellulose, starch, fat, and protein, but also the wax, 
tannin, and resin of the leaves are produced. 
The most interest, of course, is attached to the formation of nicotine, 
which alkaloid, according to Pinner, has to be considered as pyridyl-N- 
methyl-pyrrolidine. Itis probably formed from decomposition products 
of proteins and plays no further physiological role in the plant. The 
malic acid of the leaf may also participate in the synthesis of nicotine, 
since nicotinic acid can easily be reached by transformations of malice 
acid. The object of the nicotine production in the wild plant is possi- 
bly to keep off depredating enemies among the insects, but the amount 
of this poison in young plants cultivated in our climate is too small to 
kill the insects teeding on the leaves.! Even the ripe leaves, richest in 
nicotine, are attacked with impunity by certain caterpillars, grasshop- 
pers, and the “suck fly,” a heteropterous insect (Dicyphus minimus). 
The nicotine, according to Wizsman-Leyden, is contained especially in 
the cells underneath the hairs.2 Adolf Mayer found that the veins 
contain much less nicotine than the lamina. 
The fresh leaves contain relatively but little wax, resin, lecithin, 
tannin, and calcium oxalate, the latter occurring as a sandy erystal- 
line deposit, especially in mesophyll cells. The oxalic acid, as well as 
the citric and malic acids of the leaves, is probably an oxidation prod- 
uct of sugar.’ A part of these acids occurs in the form of a neutral, 
another part as acid salts.‘ The cell sap, therefore, shows an acid 
'The amount of nicotine formed depends largely upon climate and weather (cf. A. 
Mayer, Landw. Vers. Stat. vol. 38, 453 [1891]). 
2Siidd. Apoth. Zeitg., 1898. 
3’ According to Kissling the amount of oxalic acid varies in commercial tobaccos 
between 0.96 and 3.72 per cent of the dry matter; that of citric acid between 0.55 
and 8.73; that of malic acid (in form of neutral and also acid salts) between 3,49 
and 10 per cent. (Chem.-Zeitung, 1899, No. 1.) 
4Behrens (Landw. Vers. Stat. vol. 52) found from 5.79 to 9.79 per cent malic 
acid in form of soluble salts in the tobacco leaf (dry matter) and infers that it is 
the hygroscopic quality of these salts that keeps the leaves from drying up too 
easily, which thus preserve a certain softness and elasticity. The more malic salts 
are present the more ‘‘life” is in the finished tobacco leaf. Stored under equal con- 
ditions, leaves rich in malic salts may contain 3 per cent more water than leaves 
poor in them. 
