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.
For the benefit of those who have had no experience with the microscope, I will give the following directions:
Take a small portion of the starch or spice to be examined upon a clean camel’s hair brush and dust it upon a common slide, blow the excess away and moisten that retained with a drop of a mixture of equal parts of glycerine and water, or with glycerine and camphor water, and cover with a glass. It is well to have a small supply of the common starches in a series of tubes which can be mounted at any moment and used for comparison. They may be permanently mounted by making with cork borers, of two sizes, a wax cell ring equal to the diameter of the cover glass and, after cementing the cell to the slide with copal varnish thinned with turpentine and introducing the starch and glycerine mixture, fixing the cover glass on after running some of the cement over the top of the ring. A little experience will enable one to put the right amount of liquid in the cell and to make a preparation that will keep for some time. After several months, however, it is hard to distinguish the rings which mark the development of the granule, and it is better to keep it fresh.
For other purposes, the starches should be mounted in prepared Canada Balsam, or by well-known methods in which they may be preserved indefinitely, but they are scarcely visible with ordinary illumination and must be viewed by polarized light, which will bring out distinctive characters not seen as well, or not at all, in the other mounts. When mounted in the manner described, in glycerine and water, or in water alone, if for temporary use, under a microscope with one objective of equivalent focus of one-half to one-fifth inch, and with means for oblique illumination, the starches will display characteristics which are illustrated in [Figs. 2, 3, and 4]. The illustrations have been drawn from Nature; Fig. 2 gives starch stained with iodine; Fig. 3 gives shape and size of plain starch, and presence or absence of a nucleus, or hilum, and of the rings and their arrangements which can be made out. The starch is classed in its proper place.
If mounted in balsam, their appearance is scarcely visible under any form of illumination with ordinary light, the index refraction of the granules and the balsam being so similar, but when polarized light is used the effect is a striking one. (See [plates of ginger], where it is easy to distinguish all the characteristics, except the rings, the center of the cross being at the nucleus of the granule.)
The principal starches which are met with may be described as follows in connection with illustrations given, beginning with those of the arrowroot class, including potato, ginger, and tumeric.
Fig. 6. & Fig. 7. POTATO STARCH
Fig. 8. MARUNTA STARCH
Fig. 9. Fig. 10. MARUNTA