The fibro-vascular bundles are most prominent in ginger and in the barks, while in the powdered spices they are found as stringy particles. The sclerenchyma, or stone cells, as shown in Fig. 1, are common in the adulterant, especially in cocoanut shells, where may also be seen numerous spiral cells, and in the exterior coats of fibrous tissue. As to aids to distinguish these structures, the following peculiarities may be cited: [Illustration: Fig. 1. STONE CELLS Fig. 2. STARCH STAINED WITH IODINE Fig. 3. _Starch, plain_ Fig. 4. POTATO STARCH Fig. 5. _Potato_] The stone cells and fibrous tissue are optically active, and are, therefore, readily detected with polarized light, shining out in the dark field of the microscope as silver-white or yellowish bodies. The fibro-vascular bundles are stained deep orange brown with iodine, owing to the nitrogenous matter which they contain, while parenchyma is not affected by this reagent, aside from the cell contents, nor has it any action on polarized light, remaining quite invisible in the field with crossed prisms. Next to cellular tissue, starch is the most important element for consideration in the plant, which possesses an organized structure and is distinguished by its reaction with iodine solution, which gives it a deep blue or blackish-blue color, varying somewhat with different kinds of starch and with the strength of the reagent, and its absence is marked by no blue color under the same circumstances. Heat, however, as in the process of baking, so alters starches, converting them into dextrine and related bodies, that they give a brown color with iodine, instead of a blue-black; they are no longer starch, however; their form, not being essentially changed, permits of their identification, with a study of the size and shape of the granules of the hilum, or central depressions of nucleus, and the prominence and position of the rings. By polarized light and selenite, the starches of tubers showed a more varied play of colors than the cereal and leguminous starches which are produced above ground. The starches we are to consider are those of a limited number to be met with in spices and their adulterants, and one must be able readily to recognize the following: STARCH NATURAL TO SPICES AND CONDIMENTS Ginger, Pepper, Nutmegs, Cassia, Pimento, Cinnamon, Cayenne. STARCHES OF ADMIXTURES Wheat and other Cereals: Corn, Oats, Barley, Potato. Maranata and other arrowroots: Rice, Beans, Peas, Sago, Buckwheat. No one of these is complete in itself, but from the characters given, and with the aid of illustrations, the starches which commonly occur in substances which are here considered may usually be identified without difficulty.