640 SOLANACEM. 
apex, and with an entire margin. In the fresh state they are 
rather thick, green, and covered with viscid hairs and with 
small sessile glands ; after drying they are thinner, lighter or 
darker brown, or mottled with different shades 'of brown, and 
friable. The leaves have a thick, prominent midrib, branching 
under acute angles into lateral veins, which are curved near 
the margin. ‘The odour of tobacco is peculiar and heavy, and 
its taste disagreeable, bitter, and acrid. 
_ The variety rustica, Linn., is chiefly cultivated in India. 
Chemical composition.—Tobacco contains a large amount of 
salts, consisting of sulphates, nitrates, chlorides, phosphates, 
and malates of potassium, calcium, ammonium, and_ nicotine, 
and yields from 14 to 18°5 per cent. of ash. Larger amounts 
have been obtained, sometimes as much as 25 to 27 per cent. 
—a result which is probably due in some cases to dust adhering 
to the viscid glands, as was suggested by B. F. Creighton 
(1876). The other constituents of tobacco are albumen, resin 
extractive, gum, citric acid (Gowpzl), and nicotianin. 
Nicottanin was discovered by Hermbstiadt on distilling tobacco 
with water ; if separates from the distillate in the form of white 
foliaceous crystals, which have an odour resembling that of 
 seaseoneasincummes and a warm and bitterish aromatic taste. (Posselt 
"and Reimann, 1928.) Landerer (1835) obtained nicotianin 
from the dried, but not from the fresh leaves, Barral (1845) 
stated that it contains 7°12 per cent. of nitrogen. 
Nicotine or nicotia is the poisonous principle of tobacco, and 
was discovered by Posselt and Reimann (1828), It may be 
prepared by exhausting bruised tobacco with acidulated water, 
concentrating the infusion, adding an excess of potassa, and 
agitating with ether, which dissolves the alkaloid, and on the 
addition of powdered oxalic acid, nicotine oxalate, which is 
insoluble in ether, is separated (Schloesing): or, the ether is 
, the liquid neutralized with oxalic acid, evaporated 
to dryness, "and the residue exhausted with boiling alcohol 
which ‘aivolires oxalate of nicotine. (Ortigosa.) Onevaporating — 
the solution to a syrupy comsisterio’ and erred *. a 
canes and ether, an q 
