138 THITICUM. [class III. ORDER 11. 



The genus as it here stands is considered hy some authors as distinct 

 from the exotic species which are so extensively cultived as bread-corn, 

 rather than a mere division or group of the genus. One division (to 

 which all our native species helong) are small perennial or annual 

 plants, useful only as pastoral grasses, to which, except T. loliaceum, 

 they have given the name of Agropyrum. The other division, to which 

 they have retained the name of Triticum, is the cereal or corn- 

 grasses, of which there are several species cultivated in the temperate 

 regions of the globe (see page 71) as bread-corn. 



The native country of Wheat and other cereal grasses is uncertain. 

 Wheal varies considerably in its quality, and the quantity which it 

 produces, according to the climate and soil in which it is grown. Sici- 

 lian Wheat, of which there are two kinds, the thin and thick skinned, 

 according to the experiments of Sir H. Davy, contains more nutritive 

 matter than any grown in Britain ; and Wheat grown in the county of 

 Middlesex is more nutritious than that grown in the northern counties. 

 The flour obtained from the grain of Wheat by grinding it between 

 stones, is superior to any other for making into bread, owing to the 

 large quantity of gluten that it contains, which is in combination with 

 starch. These two (its principal constituents) are readily separated by 

 washing the flour or bruised grain with water, by which means the 

 starch is carried away with the water, and, if allowed to stand, settles 

 to the bottom : pressed in cloths, and gradually dried, it forms white 

 columnar masses — the starch of the shops. Starch is also obtained in 

 considerable quantities from potatoes, and this is superior to the wheaten 

 starch for domestic purposes. It also forms the greater part of the 

 nutritive matter of the difl'erent farinaceous substances which are so 

 much used during the time of sickness — such as sago, Vfhich is pro- 

 duced from several species of Palm, in many of the East Indian islands. 

 Salep is prepared from the roots of several species of Orchis, as the 

 mascula, morio, and pi/ramidalis. Tapioca, a well-known nutritive 

 substance, the cassava of the West Indies, and called by the negroes 

 manioc or magnioc, is prepared from the root of the Jatropha manihot, 

 which yields upon pressure a highly poisonous juice, used by the sa- 

 vages to envenom their spears, arrows, and darts ; and a draught of the 

 juice is the means by which the life of the condemned slaves is taken 

 away. This highly poisonous principle, however, is dissipated by dry- 

 ing, or washing the pulp of the root with water, and immediately by 

 heat ; what remains is chiefly starch, which is passed through a kind 

 of sieve and dried, and is highly nutritive. 



Gluten, the substance which remains after washing away the starch 

 from the flour, is prepared in considerable quantities in Italy, both for 

 home consumption and for exportation, and is obtained in the shops 

 under the names of macaroni, vermicelli, &c. This forms the ordi- 

 nary food in many parts of Italy, where it is sold by the yard. 



Wheat, Oats, Barley, &c. are liable to the attacks of several kinds of 



