STARCH. 23 



ent plants, so that the kind of plant from which 

 starch has been derived may be distinguished by 

 attention to the size, form, and structure of its starch- 

 granules. Thus, the granules represented in PL I. 

 fig. 3, which it will be noticed are all drawn under 

 the same power, are derived from different plants, 

 a being those of wheat-flour, in which the hilum is 

 obscure, and the rings faint ; b is a granule of West 

 Indian arrowroot, in which the hilum forms a trans- 

 verse crack ; c is a granule of potato-starch, in which 

 the hilum is a dot, and the rings are very distinct; d re- 

 presents the compound granules of the oat, the separate 

 granules being figured below ; e is a granule of lentil- 

 starch, with its long dark hilum and elegant oval 

 concentric rings ; and / represents a compound and 

 separate granule of rice-starch. It will be noticed 

 that the granules of oat- and rice- starch are angular, 

 as it is called. 



The knowledge of the peculiar forms of the starch- 

 granules is important in a practical point of view, for 

 it enables us to recognize them when mixed as an 

 adulteration with other substances, and also to distin- 

 guish the different kinds of starch from each other. 

 Thus table-mustard, as it is called, is principally com- 

 posed of the cheaper wheat- or pea-flour, which is 

 easily recognized by the structure of the starch-grains. 

 Arrowroot is considerably dearer than potato-starch ; 

 hence in trade the latter is fraudulently sold for the 

 former, the adulteration being detected with diffi- 

 culty by the eye, but easily under the microscope. 

 Again, rice is largely mixed with wheat-flour, as it 

 makes inferior flour into very white bread ; and this 

 may also be readily detected under the microscope. 

 The reader can now understand how valuable the 

 microscope is in detecting adulterations, with a know- 

 ledge of the various forms and structures of sub- 

 stances, especially with the aid of a few chemical 

 tests. 



