CHAP EER ey 
THE LIVING PLANT FORMS STARCH 
All our starch is formed by plants. Starch is one of 
the essential foods of man and other animals. It is 
also employed in many useful processes In the manu- 
facture or dressing of numerous useful articles. It 
occurs in many vegetables and other plant foods which 
we eat. Prepared starch, like corn flour, used for 
puddings, is nearly or quite pure starch. All this 
starch is made by plants. The plants use it in a 
variety of ways for food, and much of it, after being 
formed, is stored in some part of the plant for future 
use, aS in certain seeds, roots, or tubers. The potato 
tuber, for instance, is largely composed of starch. 
Tincture of iodine colours starch blue. When starch is 
wet or moist with water it is coloured blue by iodine. 
A tincture of iodine can be obtained from the drug 
store, or a few crystals of iodine may be dissolved in 
alcohol. In a test tube place a small quantity (as 
much as can be held on the point of a penknife) of corn 
flour which can be obtained at the grocery. Pour 
water into the test tube to a height of two inches. 
Hold the test tube over a flame for a few minutes to 
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