38 A STUDY OF WHEAT. 



grains found in the different varieties of wheat differ consid- 

 erably in size. The average size is about T1J Vo f an mcn m 

 diameter. Now if the specimen of flour be pure, we will have 

 only these grains, together with minute particles of nitrogenous 

 substances and occasionally broken fragments of the structure of 

 the wheat. All of which are represented by illustrations in the 

 American Miller of April, 1880. 



Potato Floiir. See figure .2. If it be not convenient to 

 obtain the commercial starch, the fresh starch grains can easily 

 be obtained by cutting a potato with a clean knife, and then 

 floating on the glass slide, with a drop of water, the white 

 substance which adheres to the side of the knife, and this will 

 be the object desired. Or you may shave off a very thin sec- 

 tion of the potato and place it in a watch crystal in a little 

 water ; the fine sediment settling to the bottom will be the 

 starch. The grains are round, irregularly oval, or egg-shaped, 

 and nearly transparent. The nucleus is not in the center of the 

 grain, but generally quite near the smaller end, and it is always 

 surrounded by numerous distinct rings or laminae. In speci- 

 mens which have been subjected to even a slight degree of 

 dry heat, there appears a black line or star-shaped mark over 

 the nucleus. The heat evaporates the moisture from the grain 

 and there must be a shrinkage on the surface to correspond 

 with the evaporation. This is the greatest over the nucleus 

 where is the greatest moisture, ;; - The grains are very irregular 

 in size, the smallest are just perceptible, and the largest are 

 frequently -^ of an inch in length, and large enough to be 

 seen with the unaided eye. A very decided cross is seen when 

 viewed with polarized light, the arms of the cross radiating 

 from the nucleus of the grain and not from the center as it 

 does in some other kinds of starches. 



This is the cheapest and therefore the most common of 

 all the substances used for adulterations both of wheat flour 

 and of the spices. There are from $800,000 to $1,200,000 

 worth thrown upon the market annually from the New Eng- 

 land States, and probably the most of it is used for adulteration. 



Potato flour is considerably heavier than wheat, so in ex- 

 amining the different layers of the little cone composed, of the 

 sediment it would be found, if present, in a layer beneath 



