340 THE BIOLOGY OF THE PIAHT 



you get the same result as yoii did without the 

 grape-sugar ? To what, then, is due the change 

 noticed in this last experiment ? 



4. Repeat the preceding experiment, using starch 



instead of grape-sugar. Do you get the same 

 result as with grape-sugar ? Why ? Can you, 

 then, by using sodium hydrate and copper sul- 

 phate, detect the presence of grape-sugar in a 

 solution ? Could you detect it by merely look- 

 ing at the solution, i. e., without the use of 

 chemicals ? 



5. Prepare some dry beans or corn as previously 



directed. Filter the contents of the test-tube 

 used into another tube, add sodium hydrate 

 and a few drops of copper sulphate, and boil. 

 "What result? Is grape-sugar present in the 

 dry seed ? How do you teU ? 



G. Tests yor albumeji {aleurone). 



1. Into a test-tube about one-third full of water 



put two or three drops of the white of an egg, 

 and shake the tube. Pour into the tube ten or 

 twelve drops of sodium hydrate. Shake again, 

 add one or two drops of a one per cent, solu- 

 tion of copper sulphate, shake vigorously to 

 mix thoroughly the contents of the tube, then 

 boil. If the deep-blue color' formed by the 

 mixture of the two reagents changes to a pur- 

 ple, either before or after boiling, the presence 

 of an albuminous substance is indicated. 



2. Repeat the above, using boiled starch in place of 



the white of egg. Do you get the purple color? 

 Why? 



3. Prepare some beans free from the testa, as was 



