476 SYSTEMATIC BOTANY. 



from which China Tea is prepared, are moderately stimulant and 

 astringent, slightly soothing and sedative, and indirectly nutritive. 

 The following are the more important plants belonging to the 

 order : — 



Frext'era theotdes — The leaves of this shrub are used as a kind of tea in 

 Panama. 



Kielmeyera speciosa — The leaves of this plant, which is a native of Brazil, 

 contain much mucilage, and are employed on that account for fomentations. 



Gordonia. — The bark is astringent 'and is therefore useful in tanning, for 

 which it is sometimes used in the United States. 



Caynellia japonica. — Numerious varieties of this species, which is a large 

 tree in its native country, are cultivated in our greenhouses, and are cele- 

 brated for the beauty of "their flowers and foliage. Tiie seeds of C. oleijcra 

 yield by expression a good salad-oil. C. Sasanqua has fragrant flowers, which 

 are said to be used in some districts to give flavour and odour to Chinese Tea. 



Thea — From the leaves of two or more species or varieties of this genus, 

 the tea which is so extensively used in this and some other countries is pre- 

 pared. Two species are natives of China, namely, Thea Bohca and T. viridis, 

 from which Ciiina Tea is obtained. Another species, Thea assaniica, fur- 

 nishes Assam Tea. There is considerable doubt, however, whether these 

 should be considered as distinct species, or only as varieties of one, owing 

 their differences to soil, climate, mode of cultivation, &c. It was formerly 

 supposed, that Black Teas could only be obtained from T. Bohea. and Green 

 Teas from T. viridis, but Mr. Fortune and others have proved, that both 

 Black and Green Teas may be made indifferently from either T. Bohea or 

 T. viridis, the differences between such teas depei.ding, partly, on the species 

 or variety of plant from which the leaves have been obtained, but more paiti- 

 cularly from the time of gathering, and mode of preparation. Tluis, Green 

 Teas, are generally prepared by drying the young leaves as quickly as passible 

 after they are gathered; then slightly heating them, after which they are 

 rolled separately or in small heaps, and then dried as quickly as possible: 

 while Black Teas are usually made from the older leaves, which, after being 

 gathered, are exposed to the air for some time ; and then, after having been 

 tossed about, are placed in heaps, where they undergo a kind of fermentation ; 

 after which they are exposed to a fire (or a short time ; then rolled in masses 

 to get rid of the moisture, and to give them a twi>ted character ; alter which 

 they are again exposed to the air, and finally dried slowly over a fire. Thus, 

 Green Tea consists of the young leaves quickly dried after gathering, so that 

 their colour, &c., is preserved, and Black Tea is the older leaves dried some 

 lime after being gathered, and after they have undergone a kind of fermenta- 

 tion, by which their original green colour is changed to black, as well as other 

 important changes produced. Several varieties of Black and Green Teas are 

 known in commerce. Thus of the former, we have Bohea, Congou, Souchong, 

 Pekoe, Caper, &c. ; of the latter, Hyson, Hyson-Skin, Twankay, Imperial, 

 Gunpowder, &c. The finer varieties of tea, are prepared from T. viridis. 

 Some teas have a particular odour, somewhat resembling the flowers of the 

 common Cowslip ; this is produced by mixing with them the dried flowers 

 of the sweet-scented olive (Oka fragrans). Other teas are scented with 

 the dried flowers of Chloranthus incoiispicuus, Aglaiu od irata, \c. 



The cultivation of the Tea-plant is now being carried on with success by 

 the East- Indian Government in certain districts of the Himalayas. A large 

 quantity of Black Tea is also now obtained from Assam. China, however, is 

 the great tea-producing country; in that part of the world, 3,')00,0 acres of 

 ground are devoted to it alone, and the total produce in 185-.', according to 

 Johnston, was 1,000,000 tons, or 2,240 millions of pounds. In the United 

 Kingdom, the consumption of Tea annually is nearly 60,000 millions of pounds, 

 or about 2G.000 tons, being at the rate of about 2 lbs. per head of the popula- 

 tion. Tea owes its chief properties to the presence of a volatile oil, tannin, 

 and an alkaloid called iheine; which is identical with caffiinc, the alkaloid 

 contained in Coff'ee. and nuaraiiine, the alkaloid of Guarana (seep. 4H3) ; 

 and closely allied to theobroniiue, the alkaloid of cocoa seeds (seep. 471). 

 Tea-leaves also contain about per cent of gluten, but this is scarcely ex- 

 tracted in any amount by the ordinary mode of making Tea. It has bei-n 

 recently proved that Tea, besides its stimulating and soothing eftects, is indi- 

 rectly nutritive, — that is to say, the theine it contains has the effect of pre- 



