[Fig. 34] is more variable in size, many of the granules not exceeding .02 millimeter while the largest reach .06 to .07 millimeter. It lacks distinctive characteristics entirely, and is the most simple in form of all starches described.
OAT STARCH
[Figs. 35 and 36], is unique, being composed of large compound masses of polyhedral granules from .12 to .02 millimeter in length, the single granules averaging .02 to .015 millimeter. It does not polarize actively, as may be seen in the figures, and displays neither rings nor hilum.
The first sign of maize or corn meal as an adulterant is the thin outer coat which becomes detached in milling and is not readily crushed. In yellow corn it has a pinkish color, and simple, longitudinal cells.
Broken rice is sometimes used as a dilutant; it may be recognized by the brilliant appearance of the hard white particles which may be picked out of the spice under a hand lens.
The two cereals named (broken rice and maize corn) are the only ones which are commonly met with that introduce starch.
Wheat bran ([Fig. 37]) is occasionally added, which can be recognized by its distinctive structural character and is better understood from an authentic specimen, which should be soaked in chloral-hydrate.
As modified cereals, we find refuse bread, cracker dust, and stale ship bread, in which the wheat starch is much changed from its original form by the heat and moisture, so that at times it might be confused with leguminous starch, but the softness of the particles and the ease with which they fall to pieces in water reveal their true name. Oil seed, oil cake, and husk ([Figs. 38, 39, and 40]) are very commonly used and are readily recognized by the peculiar structure of the outer coats of the seed. The particles, which can be usually found and selected with a dissecting microscope, should be examined in alcohol or glycerine, or a mixture of the two, as the outer coats of some seeds, such as mustard, are swollen by water and become indistinct. Many varieties of the cruciferous seeds resemble it very much, so that it is difficult to distinguish them, but it is generally recognized by the outer layer of hexagonal cells and a middle and inner coating, which consists of peculiar angular cells, the latter being much larger than the former, which are the most characteristic feature, and should be compared with seeds of known origin. After soaking in chloral-hydrate, the remaining interior layers are, perhaps, more easily made out, in some cases, after moderate bleaching with nitric acid and chlorate; the interior of this seed is not blued by iodine.
Peanut, or ground nut cake, is recognized by the characteristic structure of the red-brownish coat, which surrounds the seed, and consists of polygonal cells with peculiar saw-toothed thickening of the walls. The seed itself consists of polygonal cells full of oil and starch granules, which are globular in form and not easily confused with pepper starch. The structure of the brown membrane is best made out in chloral-hydrate, which removes the red color and leaves the fragments of a bright yellow.
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.