=196. Identification of Starches of Different Origin.=—It is often important, especially in cases of suspected adulteration, to determine the origin of the starch granules. For this purpose the microscope is the sole resort. In many cases it is easy to determine the origin of the starch by the size or the shape and marking of the grains. In mixtures of more than one kind of starch the distinguishing features of the several starches can be clearly made out in most instances. There are, however, many instances where it is impossible to discriminate by reason of the fact that the characteristics of starch granules vary even in the same substance and from year to year with varying conditions of culture. In many cases the illustrations of the forms and characteristics of starch granules which are found in books are misleading and no reliance can be placed on any illustrations which are not either photographs or drawings made directly from them. In the microscopic study of starches the analyst will be greatly helped by the following descriptions of the characteristic appearance of the granules and the classifications based thereon.[164] =197. Vogel’s Table of the Different Starches and Arrowroots of Commerce.=—_A._ Granules simple, bounded by rounded surfaces. I. Nucleus central, layers concentric. _a._ Mostly round, or from the side, lens-shaped. 1. Large granules 0.0396-0.0528 mm, _rye starch_: 2. Large granules 0.0352-0.0396 mm, _wheat starch_: 3. Large granules 0.0264 mm, _barley starch_. _b._ Egg-shaped, oval, kidney-shaped: Hilum often long and ragged: 1. Large granules 0.032-0.079 mm, _leguminous starches_. II. Nucleus eccentric, layers plainly eccentric or meniscus-shaped. _a._ Granules not at all or only slightly flattened: 1. Nucleus mostly at the smaller end; 0.06-0.10 mm, _potato starch_: 2. Nucleus mostly at the broader end or towards the middle in simple granules; 0.022-0.060 mm, _maranta starch_. _b._ Granules more or less strongly flattened. 1. Many drawn out to a short point at one end. _a._ At most 0.060 mm long, _curcuma starch_: _b._ As much as 0.132 mm long, _canna starch_: 2. Many lengthened to bean-shaped, disk-shaped, or flattened; nucleus near the broader end; 0.044-0.075 mm, _banana starch_: 3. Many strongly kidney-shaped; nucleus near the edge; 0.048-0.056 mm, _sisyrinchium starch_: 4. Egg-shaped; at one end reduced to a wedge, at the other enlarged; nucleus at smaller end; 0.05-0.07 mm, _yam starch_: _B._ Granules simple or compound, single granules or parts of granules, either bounded entirely by plain surfaces, many-angled, or by partly round surfaces.