THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. VI. 



Washington, D. C, Jdnb, 1885. 



No. 6. 



The Microscopicnl Examination of 

 Tea. 



Tea is the leaves of T/fca sinensis^ 

 an evergreen, native in China, Japan 

 and Eastern India. A few years ago 

 teas were greatly adulterated in China, 

 and more or less after importation, 

 but at the present time it is not an 

 casv matter to find teas adulterated 

 with other leaves. The leaves that 

 have been used, according to testi- 

 monv more or less trustworthy, are 

 the willow, elder, sloe, and many 

 others, and exhausted tea-leaves. 



Green and black teas are obtained 

 from the same plant, the differ- 

 ences in appearance and flavor being 

 due to the methods of preparation. 

 To give the leaves an attractive ap- 

 pearance they are sometimes faced 

 with coloring matters, such as plum- 

 bago, Prussian blue, soapstone. turme- 

 ric and other harmless compounds. 

 Such additions cannot be regarded as 

 adulterations ; but occasionally sand 

 or solid particles in excessive quan- 

 tity are found, obviously added to in- 

 crease the weight. 



The microscopical charactei's of 

 the tea-leaf are such as to enable the 

 obsen'er to distinguish even small 

 fragments w'lXh certainty. The leaves 

 should be treated with hot water and 

 then spread out on a smooth surface. 

 s.uch as a plate of glass, and examined 

 with a hand-lens to make out the ve- 

 nation. This is quite peculiar in the 

 tea-leaf, the veins spreading from the 

 midrib, forming closed, oblong loops 

 within the margin of the leaf, and ob- 

 long meshes on either side of the 

 midrib. 



The margin is distinctly toothed, 

 and more or less emarginate at the 



apex. Each serration ends in a short 

 spine, more or less curved inwards. 



For perfectly satisfactory examina- 

 tion of the microscopic structure the 

 leaves require some preparation, since 

 they are too thick, and too close in 

 texture, to make good objects for 

 study in their natural condition. 

 However, one who is familiar with 

 their structure can identify the leaves 

 very well after they are softened in 

 water and prepared in glycerin. 



The under siu-face of the tea-leaf 

 is shown in Fig. 14. It consists of 

 numerous stomata among the curious. 



Fig. 14. — Under surface of Tea-leaf. 



irregular, outlined cells, and simple 

 hairs. The upper surface bears no 

 stomata. and the cells are similar to 

 those of the under surface, but 

 smaller. The interior of the leaf is 

 made up of fibro-vascular tissue, and 

 cells filled with chlorophyll, the latter 

 shown at A Fig. 15. There are also 

 some peculiar branched cells like that 

 shown at c in the same figure. 



To study the epidermis to advantage 

 it may be readily removed by boiling 

 in water acidified with nitric acid. 

 The epidermis is thus made to peel oft' 



