THE FLOWERING PLANT SEEDS 339 



vide the contents into two parts. Test the first 

 part with a drop of iodine. Does the bean con- 

 tain starch ? How do you tell ? Filter the sec- 

 ond part until perfectly clear, and test the fil- 

 tered fluid with iodine. Is starch present? 

 Does starch dissolve when boiled ? 

 5. Test the testa for starch. Does it contain any 

 starch? In what part of the seed is starch 

 stored ? Put a drop of iodine on the surface 

 of an uninjured cotyledon of a soaked bean. 

 "What result? Explain. Cut the end off the 

 cotyledon, and apply a drop of iodine to the 

 cut surface. What result? In what part of 

 the cotyledon is the starch stored ? 



h. Tests for grape-sugar. 



1. Put some grape-sugar (glucose) into water in a 



test-tube. Does the sugar dissolve? Do you 

 think that if a plant-cell contained grape-sugar 

 it would be dissolved in the watery fluid (cell 

 sap) forming the vacuole? Compare with the 

 starch. Test the sugar with iodine. Do you 

 get the same reaction as with starch ? Why ? 



2. Fill a test-tube one -fourth full of water, add an 



equal amount of sodium hydrate, and shake 

 the tube. What change ? Add two or three 

 drops of a one per cent, solution of copper sul- 

 phate. What change ? Shake the tube vigor- 

 ously. What change? Boil the contents of 

 the tube for a minute or two. What change ? 



3. Into a test-tube one -fourth full of water put a 



pinch of grape-sugar, then add the sodium hy- 

 drate and copper sulphate as before, and shake 

 the tube. Then boil for a minute or two. Do 



