806 ECONOMIC BOTANY. 



cultivated from ancient times for coloring yellow; but 

 siuce the introduction of Quercitron it has not been so 

 much used. The important constituent is Luteolin, con- 

 sisting of yellow, prismatic crystals, soluble in alcohol ; the 

 solution is bitter and the reactioi) acid. 



297. The Tea-plant, Camellia chinenses (family Tunv- 

 strcendaeecB), has been cultivated, for ages, and its native 

 country is now no longer known. It is an evergreen 

 shrub or very small tree, generally kept dwarf by pruning. 

 The branches are very numerous, bearing elliptical or 

 lanceolate leaves, which are two or three inches in length. 

 The plants yield a smaU picking when three years old, but 

 the maximum yield is in the eighth or tenth year. The 

 leaves are carefully picked, heated in pans, and rubbed 

 with the hands into the form they retain. The processes 

 of heating, airing, pressing, rolling, and drying are con- 

 tinued alternately till the desired changes take place in 

 the leaves. The rapidity of this operation and the age of 

 the leaves when picked determines the quality of the 

 tea; young leaves, quickly prepared, give the best green 

 teas. Old leaves, subjected to a less rapid operation, yield 

 the black teas. Among the many constituents found by 

 analysis, may be mentioned carbo-hydrates, albuminoids, 

 tannin, caffein, aromatic oil, and mineral substances. Tea 

 (an infusion of the leaves) has been used by the Chinese 

 as an exhilerating beverage for centuries. Recently it has 

 found its way into nearly all countries, and is used almost 

 universally now by rich and poor. 



298. Tobacco, Niaotiana Tabacum (family SolanaeecB), 

 was used by the Indians long before America was dis- 

 covered by Columbus, for in old Indian mounds smoking 

 utensils have been found. It was taken to Spain by 



