THE MICROSCOPE AS DETECTIVE 



larger and larger. The dark spot is called the 

 hilum and the rings are known as striations. In the 

 potato starch grain the hilum is not central and the 

 striations are not circular. Wheat has large and 

 almost round grains without a hilum or striations, 

 those of Barley are very similar but smaller and not 

 so uniformly round. Rye grains are frequently 

 cracked and often have ragged edges. 



A very large number of these objects may be 

 examined, for it is useful to know their structure 

 if one's object be to examine various foods; from 

 the point of view of beauty, when examined with 

 a polariscope, they have few rivals. Maize starch, 

 which is to be found in most houses under the name 

 of corn flour consists of two kinds of grain. Some are 

 many sided and angular, all of one size and without 

 striations, they are also split at the centre ; the other 

 grains are rounded, of various sizes and are never like 

 the angular grains grouped together. The former 

 come from the horny part of the maize, the latter 

 from the floury portion. 



Rice starch is also many sided and angular, 

 almost crystal like; there are, however, never any 

 rounded forms and this serves to distinguish it from 

 maize starch. The shape of Arrowroot starch 

 grains varies according to the plant from which it 

 is derived, for this substance does not all come from 

 one kind of plant but, whether the grains be pear 

 shaped, hammer shaped, triangular or dumbell 

 shaped they all show striations and an x-shaped 

 split in place of a hilum. Tapioca starch grains are 



141 



