Thea Sinensis L.
Part 1. USD 21st 1926.
U.S.D. 21st 1926.
Tea. The, Fr. Thee, G. Thea sinensis L. (Camelia Thea Link) (Fam. Theacete)
Tea is an evergreen shrub. It has numerous alternate branches, furnished with elliptic-lanceolate, or obovate-lanceolate, short-petiolate, acuminate leaves, which are serrate except at the base, smooth on both sides, occasionally pubescent beneath, green, shining, pinnately veined and having a prominent midrib. They are two or three inches long, and from half an inch to an inch in breadth. The flowers are either solitary or supported, two or three together, at the axils of the leaves.
They are of considerable size, not unlike those of the myrtle in appearance, consisting of a short green calyx with five or six lobes, of a corolla with from four to nine large unequal snow-white petals, of numerous stamens with yellow anthers and connected at their base, and of a pistil with a three-parted style. The fruit is a three-locular and three-seeded capsule.
There are two principal varieties of T. sinensis, viz. viridis Pierre (T. viridis L.), which is a large spreading shrub, having light green lanceolate leaves from 12 cm. long to 4 cm. wide; and a second variety, Bohea Pierre (T. Bohea L.), which is an upright shrub with dark-green elliptical leaves 6 cm. long and 3 cm. wide. The flowers of the latter occur in groups of two or three, whereas in viridis they are single.
There are a great many varieties of tea, on the market, and their trade value is influenced by the peculiarities of mother plant and climate, and the degree of ripeness and preparation of the leaves. As a rule only the youngest leaves are gathered. The so-called black and green teas are due to the method of preparation of leaves. In the first the chlorophyll is destroyed, whereas in the latter it is unaffected. Winton gives the following characters as common to all tea leaves:
The firm, rather thick texture; the glossy upper surface; the short stem into which the base of the leaf tapers; the thick margins, rolled a little towards the inner surface, with cartilaginous teeth; the veins which branch from the midrib at angles usually greater than 45 degrees, and at some distance from the margin form loops uniting adjoining ribs. The teeth on the margin of the leaf are shrunken multicellular glands which break off readily from the old leaves." (For discussion of microscopical characteristics, see Winton and Moeller, The Microscopy of Vegetable Foods.
The tea plant is a native of China and India, and is cultivated in both countries, but most abundantly in the former. It is also cultivated in India (Assam), Ceylon, Java and in South Carolina. In Japan it forms hedge rows around the rice and corn fields; in China, whence immense quantities of tea are exported, whole fields are devoted to its culture. It is propagated from the seeds. (An elaborate article on tea, with methods of cultivation, etc., by Wm. B. Marshall, will be found in A. J. P., 1903, p. 79.)
The odor of the tea leaves themselves is very slight, and it is customary to mix with them the flowers of certain aromatic plants, as those of the orange, different species of jasmine, the rose, Osmanthus fragrans Lour. (Olea fragrans Thunb.), of the Oleacece, and Camellia Sasanqua Thunb., in order to render them pleasant to the smell. The flowers are afterwards separated by sifting or otherwise. (See P. J., xv, 112.) Under the name of flowers of tea was at one time sold a waste product consisting of the hair of young leaves, but the flowers themselves have been used to make a beverage. (P. J., lxxi, p. 453.)
Bush Tea and Honig Thee, used at Cape Colony, South Africa, as a substitute for tea, are the dried leaves and tops of several species of Cyclopia, among which are C. subtemata Vog., C. latifolia DC., C. genistoides Vent. (Fam. Leguminosae.) According to the analysis of Henry G. Greenish, they do not contain theine, but a glucosidal body, cyclopin, C25H28O13. (P.J, xi, 549.)
The numerous commercial varieties of tea may be divided into two great groups, Green Tea and Black Tea. The differences between black tea and green tea are due chiefly to the methods of their preparation. In making green tea, the leaves after being dried for a short time in the sun are heated in open pans with continual agitation, somewhat after the manner of roasting coffee.
In the case of black tea (formerly called Bohea), the dried leaves are rolled either between the hands or between two flat surfaces, during which process they acquire their characteristic twisted shape and some of the juice is pressed out; they are then piled on mats and allowed to stand exposed to the air at a temperature of 35 to 40� C. for about twelve hours.
During this time they undergo a sort of fermentation, which is signified by a change in the color of the leaf from green to red and finally to the dark brown of commerce. It is believed that this change is due to the effect of an oxydase which is called thease. As a result of this treatment some of the aromatic principle of the tea leaf is volatilized and a portion of the tannic acid is destroyed. As a rule, therefore, black tea has a somewhat less fragrant odor and a less astringent taste than green tea. Green tea is sometimes artificially colored by means of Prussian blue or other coloring matter. A sophisticated tea is largely exported from China, consisting of powdered tea mixed with sand and other earth, and agglutinated with gum; that which is to pass for black being colored with plumbago, and the green with the coating above referred to. On analysis, these teas were found to afford from 35 to 45 per cent, of ash, while the genuine yields only 5 percent. A very full account of the adulteration of tea and the methods for the detection of the same
may be found in Allen, Com. Org. Anal., 2d edition. See also Rehfous, Pract. Drug., Nov., 1917, The analyses below1 by Y. Kozai (Bulletin No. 7, Imperial College of Agriculture, Japan) have a special value, owing to the author's knowledge of tea manufacture. Unusual precautions were taken in sampling the leaves, to insure strictly parallel specimens being taken. The figures refer to the moisture-free leaves in each case.
The most important principle in tea is the substance discovered by Oudry and by him called theine, but which is now known to be identical with caffeine (see Caffeina). In 1888 Kossel showed the presence of small amounts of a related principle theophylline (dimethylxanthin). Traces of theobromine have also been reported. In 1848 Rochleder isolated a yellowish amorphous substance which he called boheic acid, but whose chemical identity seems doubtful.
Tea also contains a notable proportion of tannin (from 5 to 20 per cent.) which is very similar to, if not identical with, that of oak bark. There are present also traces of a volatile oil to which is due the characteristic odor. This oil is of a lemon yellow color and easily resinified on exposure to air. The proportion of caffeine found in tea varies considerably, the general range being from about 1 to 5 per cent.
Tea is astringent and gently excitant, and exerts a decided influence over the nervous system, evinced by the feelings of comfort and even exhilaration which it produces, and the unnatural wakefulness to which it gives rise when taken in unusual quantities or by those unaccustomed to its use. It is almost exclusively used as a beverage. Taken moderately, and by healthy individuals, it may be considered as practically harmless; but long continued in excessive quantity it is capable of inducing unpleasant nervous and dyspeptic symptoms.
Green tea is decidedly more injurious in these respects than black, and should be avoided by dyspeptic individuals, and by those whose nervous systems are peculiarly excitable. It is rarely used as a medicine, but the infusion is popularly employed to relieve neuralgic headaches.
Tea Oil. Tea-seed Oil. The seeds of various species of Camellia, especially the C. drupifera Lour. (C. oleifera Wall.) and the G. Japonica L., yield on pressure a pale yellow fixed oil which is used by the Chinese both as fuel and food. It has been used in England as an adulterant of olive oil. The seeds of the Camellia Japonica, which sometimes appears in our gardens as an ornamental shrub, are said to contain a poisonous glucoside camellin.
Part 2. H.F.Macmillan, F.L.S. A.H.R.H.S.
Image � : Manual of Cultivated Plants by L.H.Bailey.
And the staff of the Bailey Hortorium. Cornell University.
or Cha-e ; Thay-gas or Thay-kola, S ; Tey-ile, T.
The China Tea (var. Bohea) is distinguished by its squat, straggling habit and comparatively thick leaves ; it is the kind chiefly grown in China and is cultivated on some of the higher estates in Ceylon, being hardier than, but not so productive as, the Indian varieties referred to.
The " Assam Hybrid " is considered to be a natural hybrid between the " Assam " and " China " varieties. Left to itself the " Assam Tea " is an erect tree, 30 - 40 ft. high, but in cultivation it is topped early at a height of about 2 ft. and kept as a bush, not being allowed to grow higher than about 4 or 5 ft., except of course for seed purposes. The Tea plant normally lives to a great age. The oldest Tea in continuous cultivation in Ceylon is over 80 years old, and shows no falling off in quality or yield.
Tea has been cultivated from time immemorial in China and Japan. Its cultivation in Ceylon on a commercial scale may be said to date from 1867, although the earliest record of its introduction to the Botanic Gardens goes as far back as 1839 for " Assam Tea," and to 1824 for " China Tea."
Tea-leaf was first introduced into England about 1658, from Holland, when it cost �3 per lb. The plant is now extensively grown in S. India, Bengal, Assam, Java, Ceylon, etc. In the latter country the export rose from 23 lb. in 1873 to nearly 244 million lb. in 1931, and about 570,000 acres are now under the product. China is considered to be the largest tea-producing country, but the bulk of its production is consumed locally. In recent years, Tea has been successfully established on a commercial scale in Natal and E. African colonies.
Cultivation. The plant is adapted to a wide range of climate and soils, provided the rainfall is abundant (not less than about 85 in.) and evenly distributed. In which should be of a humus nature. Humus may be supplied by means of green-manuring, or by thinly inter planting with quick-growing leguminous trees which can be lopped frequently, the twigs and leaves being lightly forked into the ground. (See Green Manures.) Manuring periodically, either with artificial or cattle manure, is necessary in order to maintain the bushes in a healthy and vigorous condition. The cost of manuring is usually considered to average about one penny to 1� penny. per lb. of made tea, or an average of about �3 per acre per annum.
Propagation, planting, etc. Tea seed is usually sold by the maund (80 lb.), which contains from 18,000 to 20,000 seeds, according to jat (variety), the better the jat the heavier the seed. Manured and well-cultivated seed-bearing trees generally yield the heaviest and best seeds. A maund should produce from 14,000 to 18,000 plants, or sufficient to plant 3 acres at 4 x 3 ft. spacing, or 4 acres at 4 x 4 ft., making a liberal allowance for failures.
Seed is sown in nursery beds at distances of 4 in. each way, the beds being shaded by fern fronds or Grevillea leaves fixed in the ground slanting-wise. It is best, however, to raise plants in small plant-baskets or bamboo-joints, as these may be planted out direct without injuring the roots.
Efforts have been made to propagate Tea by root-cuttings and other vegetative means, but, though theoretically much to be desired, these methods have so far not been found a commercial success. In about 10 months from sowing, the seedlings should be about 12 in. high and ready for planting out in the field. Holes being made in lines, the plants are set out at distances of about 4 x 3 ft., 4 x 4 ft., or 5 x 4 ft., then shaded, and watered when necessary, until well established. About 18 months after planting, the plants are topped, i.e. cut back to about 15 in. from the ground, so as to induce a bush form.
Plucking, yield, etc. The first crop of leaf is obtained in the third year in the low-country, being a year or so later at higher elevations. At low elevations plucking takes place about once in 8 or 10 days, and at the higher altitudes once in 2 or 3 weeks, according to elevation. Plucking is usually done by women or boys, and consists in nipping off by hand the tender end leaves with bud and shoot; taking two leaves with shoot and end bud constitutes fine plucking and forms good quality tea, while four leaves and a bud forms coarse plucking and yields tea of a lower quality.
Pluckers will gather from 30 to 80 lb. or more green leaf a day, according to the condition of the field and the activity of the pluckers. 4 lb. of green leaf will produce 1 lb. of made tea. When the bushes stop " flushing," they are pruned back severely, this being necessary at intervals of about 16 - 20 months in the low-country and about 3 years up-country. When in full bearing, at 7 or 8 years old, the crop of made tea may, according to elevation, nature of soil, and degree of cultivation, be from about 400 lb. to 1,000* lb. or more per acre ; 700 lb. is considered a good average yield. Altitude is an important factor, for on this the quality of the tea largely depends. High-grown tea, say from 5,000 to 6,000 ft., commands the highest price and is generally used for blending with lower grades from low elevations.
* On Mariawatte Estate, Gampola, Ceylon, a field of over 100 acres gave an average of 1,357 lb. per acre for over 20 years.
Curing (Black Tea). The leaf being brought to the factory, it is withered on tiers of Hessian screens in drying sheds, through which hot air from furnaces is driven ; it is then rolled by means of rolling-machines, during which the process of fermentation or oxidation sets in.
Fermentation is continued by spreading the mass of bruised leaf for 1 or 2 hours in a damp, cool atmosphere. Firing is done in drying machines, then sifting, by means of which the tea is simultaneously sorted into grades, as Souchong, Pekoe-souchong, Orange-pekoe, Broken orange-pekoe (the best-quality), and Dust or Fannings. It is then packed into lead-lined chests of uniform sizes for export. A full-size chest contains 80-100 lb.; a � chest, 40-50 lb.
Green Tea, as distinct from black or ordinary tea, is made by subjecting the green leaf at once to a process of steaming in a revolving cylinder, and afterwards by rolling, drying, etc., the processes of withering and fermentation being omitted. The grades are known as Hyson, Young Hyson, and Gun-powder. China teas are usually made on this principle. There is a certain demand for China or Green Tea in some countries, notably the United States, and Ceylon manufactures and exports a considerable quantity to meet this demand.
Brick Tea. (Russian Tea) A cheap and coarse tea, made in China and used largely in Tibet, Mongolia and Siberia, where it is held in high repute and often used as barter. It is made in two forms, one of which consists of twigs and leaves of the tea plant, pressed with a glutinous substance and dried in moulds ; the other is made up of the finer sittings and dust of ordinary tea compressed into slabs. The latter in consumed chiefly in Russia, and is prepared in various ways for use, a small piece being chipped off and either brewed like ordinary tea, or boiled, stewed and flavoured with salt, butter, etc.
Leppet or Leptet Tea - is prepared in Burma and the Shan States, where it is used as a vegetable rather than a beverage. It consists of green tea-leaves pressed and preserved on the principle of a silo, these being afterwards prepared for use by mixing with garlic, salt, oil and other ingredients.
Soluble Tea. A process was invented by the late Mr. Kelway Bamber, Ceylon Government Chemist, by which the essence of tea was extracted and rendered available in a concentrated, soluble, fine powder form, known as " Soluble Tea." Though it had much to recommend it, especially for travelers, it was not a commercial success.
Tea cider is a name given to an effervescent, sub-acid and refreshing beverage made from tea in India, Ceylon, Java, etc., and containing about 2% of alcohol. It is sometimes made when Tea does not command an economic price.