Linseed cake is distinguished by the fact that its husk is made up of one or two characteristic elements. The outer coat, or epidermis, is colorless and swells up in water, forming a mucilage, like the mustard seed. Beneath this is a layer of thin, round, yellow cells, while the third is very characteristic and consists of narrow and very thick-walled dotted vessels; next to these is an inner layer of compact polygonal cells, with fairly thin, but still thickly dotted, white walls and dark-brown contents containing tumeric. The endogen and embryo are free from starch and will not color yellow by potash, as is the case with mustard and rape seed cake. [Illustration: Fig. 35. OAT STARCH Fig. 36. _Oats_ Fig. 37. WHEAT BRAN Fig. 46. POWDERED ALLSPICE SHOWING PORT WINE CELLS. (A) STARCH] Cocoanut shells are often used, and have numerous, both long and short, stone cells and spiral vessels from this fibrous tissue; the long stone cells having thinner walls than the shorter cells, all of which are readily seen after bleaching. When the shells are roasted, they refuse to bleach, and it is then only possible to class the particles, on which the reagents do not act, as roasted shells or charcoal, which are frequently used in pepper to give desired color to material rendered too light by white adulterants. Buckwheat, after bleaching, shows a preponderance of tissue made up of long, slender, and pointed sclerenchyma cells and a smaller amount of reticulated tissue, resembling the cereals somewhat and cayenne pepper. Portions of the interior of the seed are also visible and consist of an agglomeration of small hexagonal cells which originally contained starch. The starch is readily recognized by its peculiar characteristics. The sclerenchyma is, of course, optically active and forms a beautiful and distinctive object with polarized light. Sawdust of various woods may be recognized by the fragments of various spiral and dotted vessels and fibrous material which are not found in spices or in other adulterants. Rice bran is made up prominently of two series of cells at right angles to each other, which make up the outer coats of grain, the structure being best made out after soaking in chloral-hydrate; the cells of one series are long, small, and thin-walled, and are arranged in parallel bundles; the others have very much thicker walls and are only two or three times as long as they are broad. Clove stems are distinguished by their peculiar yellow dotted vessels and their large and quite numerous cells, neither of which is seen prominently in the substances which are adulterated. The peculiarities of adulterants should be carefully confirmed and the eye trained by practice so as to become accustomed to recognizing their structure by a study of the actual substance.