plished by a careful examination of the shape and character of the leaves. For this purpose the dried leaves are opened out by soaking a short time in hot water, after which they are spread upon a glass plate, and examined by the aid of a magnifying-glass.

The genuine tea leaf (Fig. 73) is very characteristic, and is readily distinguished from other leaves. It is oval or lanceolate, 5 to 8 cm. long

and 2 to 3 cm. wide. It is short-stemmed, somewhat thick and fleshy, attenuated at the bottom and usually pointed at the top. At a certain height from the base, from a third to a quarter up, the smooth or wavy border becomes peculiarly, though not deeply, serrated in a regular manner, the serrations, which are hook-shaped, continuing to the tip of the leaf. Mature leaves always show these serrations, but they are somewhat obscure in young leaf buds. The latter, however, are rarely found in this country. The veins extend outward from the central rib nearly parallel to each other, but before reaching the border, each bends upward to form a loop with the one above.

Foreign leaves, said to be used as adulterants, are those of the willow, poplar, elder, birch, elm, and rose, but the writer has never found any of these in tea. All of them differ materially from the genuine tea leaf, and if foreign leaves are apparent in a sample under examination, they should be compared with various leaves collected by the analyst for the purpose.

FIG. 73.-The Leaf of
Genuine Tea.

Stems and Fragments.-These, as well as "tea dust," are apparent by an examination of the leaves, opened out in hot water as explained above. The ash of tea stems and dust is abnormally high.

Besson* and Deuss † oppose fixing a maximum limit for stems on the ground that the more expensive sorts often contain more stems than the cheaper. This is due partly to methods of gathering and partly to the presence of siftings with low stem content in the cheaper grades. The term "lie tea" is applied to an imitation of tea, consisting of

*Chem. Ztg., 39, 1915, p. 82. † Chem. Weekbl., 13, 1916, p. 66.

fragments, stems, and tea dust, mixed with foreign leaves, mineral matter, gum, etc. The ash of such "tea" has been found as high as 50%. Such imitations are now almost unknown. Make-weight substances, such as brick-dust, iron salts, metallic iron, sand, etc., have been found in tea. If present, they are to be found in the sediment, obtained on shaking out the tea in water.

Added Astringents. Catechu is sometimes said to be added to tea to give it increased astringency, especially to such tea as has been adulterated by the addition of exhausted tea. Hagar's method for detecting catechu is as follows:

A hot-water extract of the tea (1 to 100) is boiled with an excess of litharge and filtered. To a part of the filtrate, which should be perfectly clear, nitrate of silver is added. If catechu be present, a yellow flocculent precipitate, rapidly becoming dark-colored, is formed. treated in like manner gives a gray precipitate.

*

Pure tea

Spencer adds, instead of silver nitrate, a drop of ferric chloride to the clear filtrate. With catechu a green precipitate is formed.

As a matter of fact the worst forms of tea adulteration, such as the actual substitution of foreign leaves, once so commonly practiced, are now extremely rare in this country and have been for some years, by reason of the careful system of government inspection in force at the various ports of entry. The greater portion of the tea on our market to-day is genuine, but fraud is practiced to a considerable extent by the substitution of inferior grades for those of good quality. This form of deception is in many cases beyond the power of the analyst to detect, and properly comes within the realm of the professional tea-taster.

Tea Tablets. Finely ground tea of varying quality is sometimes pressed into tablets, to be used by travelers and campers for preparing a beverage, by simply dissolving in hot water.

The composition of one of these preparations sold under the name of Samovar Tea Tablets, analyzed by the Mass. State Board of Health, is as follows:

Microscopical Structure of Tea.-The powdered tea may be examined directly in water-mount. Schimper recommends treating the powdered tea with chloral hydrate or potash lye, to render it more transparent.

By far the most characteristic element is the peculiarly shaped sclerenchyma, or stone cell, st, Fig. 74, entirely unlike anything to be found in other leaves. These cells are very irregular in form, being sometimes star-shaped, sometimes branched, almost always with deeply wrinkled sides,

FIG. 74.-Powdered Tea under the Microscope. X 160. g, end of leaf nerve; p, chlorophyll parenchyma; st, stone cells; h, hairs. The tissues were warmed in potash to render transparent. (After Moeller.)

and often with sharp points. In most foreign leaves such sclerenchyma cells are lacking, but they are abundant in all genuine tea leaves, excepting rarely in the very young leaves, where they are sometimes not fully developed. They are especially numerous in the main vein and in the stem. They may be seen to best advantage in a section of the stem, or midrib, made parallel to the surface of the leaf. To make such a section, soak the leaf first in water, and afterward. dry in alcohol. The interior of the leaf is composed chiefly of ground tissue, having rounded cells full of chlorophyll grains and the fibro-vascular bundles of the veins.

Other important characteristics are the peculiar hair growth on the under epidermis, B, which is apparent in nearly all teas, also crystal rosettes of calcium oxalate, which are nearly always present, even in fragments of tea leaves, but not in all foreign leaves. The peculiar structure of the lower epidermis, B, with its numerous stomata is also to be noted. See Figs. 189 and 190, Pl. XVIII.

COFFEE.

Nature of Coffee. Coffee is the seed of the Coffea arabica, a tree which, when under cultivation, is not allowed to exceed twelve feet in height, but when wild sometimes reaches a height of twenty feet. It is indigenous in Southern Abyssinia, and was cultivated in Arabia in the sixteenth century, and in the East Indies in the seventeenth, afterward being introduced into the West Indies and South America. The coffeebeans are usually inclosed in pairs in the berry, being plano-convex with their flat sides together but in "pea berry" coffee only a single, rounded bean is present.

When the ripe fruit is gathered, it is first dried and then freed from the hulls, usually by machinery, or, in the West Indies, the green berries are "pulped" or "hulled " under water by a peculiar macerating machine. The raw beans are roasted, and afterwards ground for preparing the infusion.

The principal varieties now on the market are true or Arabian Mocha produced in the Yemen district and shipped from the port of Aden, Abyssinian or long berry Mocha, Java produced on the island of Java under government supervision, Rio and Santos, the leading Brazilian varieties shipped from the ports of Rio Janeiro and San Paulo respectively, Maracaibo a Venezuelian coffee, and Bogota produced in Colombia. Porto Rican and other West Indian varieties, also the product produced in the islands of the Pacific, often shipped under the name of Java, and various African coffees, are of considerable importance.

Brazil furnishes more than half the world's supply of coffee, and nearly 75% of that consumed in the United States.

Constituents of Coffee.-Most of the coffee in the retail market is roasted, being sold either in the whole bean or ground.

The chief constituents of raw coffee, besides water, are oil, cellulose, sugar, pentosans, dextrins, "caffetannic acid" (chlorogenic and coffalic acids), protein, caffeine, coffearine (an alkaloid), and ash.

During roasting the sugar is largely caramelized, the caffetannic acid reduced, the bean rendered more brittle, and certain flavors are developed. Various substances have been named as products of roasting. Of these caffeol, a volatile oily substance, has long been considered the chief aromatic constituent, but its identity is now disputed. Several authors have detected pyridine. There is a slight loss of caffeine during roasting.

The following summary of analyses of coffee of various kinds made by König show in general its composition:

The change in composition that takes place in roasting coffee is well shown by the following figures, which give the mean of analyses by König of four samples of coffee before and after roasting:

The following are analyses of common varieties of roasted coffee, also of coffee substitutes and adulterated coffee made by Lythgoe:†

* U. S. Dept. of Agric., Div. of Chem., Bul. 13, p. 904.

† An. Rep. Mass. State Board of Health, 1904, p. 320. U. S. Dept. of Agric., Bur. of Chem., Bul. 90, pp. 43-45.