. The microscopy of vegetable foods, with special reference to the detection of adulteration and the diagnosis of mixtures . ce ofthe leaf. DIAGNOSIS. After heating to boiling in water the leaves may be spread out andexamined. Even quite small fragments can be recognized by their tex-ture, venation, dentation and other macroscopic characters. The chiefmicroscopic elements of value in diagnosis are the epidermal cells, thegeniculate hairs and the idioblasts. Tea Adulteration. Gross adulteration, such as the addition ofexhausted leaves, foreign leaves and mineral make-weights, is seldompracticed
. The microscopy of vegetable foods, with special reference to the detection of adulteration and the diagnosis of mixtures . ce ofthe leaf. DIAGNOSIS. After heating to boiling in water the leaves may be spread out andexamined. Even quite small fragments can be recognized by their tex-ture, venation, dentation and other macroscopic characters. The chiefmicroscopic elements of value in diagnosis are the epidermal cells, thegeniculate hairs and the idioblasts. Tea Adulteration. Gross adulteration, such as the addition ofexhausted leaves, foreign leaves and mineral make-weights, is seldompracticed at the present time. Low-grade teas often contain tea stems, 45 ALK/ILOIDAL PRODUCTS. and sometimes tea fruit. Facing, although objectionable, is not usuallyregarded as an adulteration.^ Exhausted Tea. Leaves which have been used once for the prepara-tion of the beverage are said to be collected in England, Russia, andChina, impregnated with catechu or caramel, and prepared in imitationof genuine tea. This worthless product has the same microscopicappearance as genuine tea, but can often be detected by chemical means,. Fig. 358. Tea. Tissues of leaf isolated by warming in alkali and squeezing wnth coverglass, g spiral vessels of nerves; p chlorophyl parenchyma; st stone cells; h hairs. X160. (MOELLER.) particularly determinations of hot-water extract, tannin, total and water-soluble ash. Tea Fruit. Soltsien has reported several cases of adulteration witlithe dried fruit. Winton found in a sample sold in Connecticut percent of this adulterant. Tea Stems. Tea often contains a small amount of stems as an acci-dental impurity. A considerable amount indicates adulteration. Z,/c Tm consists of tea leaves and other refuse made into lumpswith starch-paste. These lumps fall apart on soaking in water. Mineral ^^lake-weights, including soapstone, gypsum, iron dust, andsand, are detected by chemical analysis. Facing. A large part of the green tea and mucli of the black tea isfaced, o
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