STORAGE OF FOOD IN THE SEED 15 



17. Starch — Most common seeds contain starch. Every 

 one knows sometliing about the appearance of ordinary 

 commercial starch as used in the laundry and as sold for 

 food in packages of cornstarch, ^^^hen pure it is charac- 

 terized not only by its lustre, but also by its peculiar 

 velvety feeling when rubbed between the fingers. 



18. The Starch Test. — It is not always easy to recog- 

 nize at sight the presence of starch as it occurs in seeds, 

 but it may be detected by a very simple chemical test, 

 namely, the addition of a solution of iodine. ^ 



EXPERIMEXT V 



Examination of Familiar Seeds with Iodine. — Cut in two with a 

 sliai'p knife the seeds to be experimented on, then pour on each, drop 

 liy drop, some of the iodine solution. Only a little is necessary ; 

 sometimes the first drop is enough. 



If starch is present, a blue color (sometimes almost black) wiE 

 appear. If no color is obtained in this way, boil the pvilverized seeds 

 for a moment in a few drops of water, and try again. 



Test in this manner corn, wheat (in the shape of flour), oats (in 

 oatmeal), barley, rice, buckwheat, flax, rye, sunflower, four-o'clock, 

 morning-glory, mustard seed, beans, peanuts. Brazil-nuts, hazelnuts, 

 and any other seeds that you can get. Report your results in tabu- 

 lar form as follows. 



MrcH Stakch Little Starch Xo Starch 



Color : blackish or Color : pale blue or Color : brown, orange, 



dark blue greenish or yellowish 



1 The tincture of iodine sold at the drug-stores will do, but the solution 

 prepared as directed in the Handbook answers better. This may he made up 

 in quantity and issued to the pupils in drachm ^ials, to he taken home and 

 used there if the experimenting must he done outside of the laboratory or the 

 schoolroom. - May be a home experiment. 



