42 EXPERIMENTAL PLANT PHYSIOLOGY. 



EXPERIMENT 48. 



MICROCHEMICAL TEST FOR STARCH. 



Decolorize some filaments of Spirogyra, or leaves of Funaria as 

 above, and place on a glass slide in a drop of chloral hydrate 

 (chloral hydrate 5 parts, water 2 parts). Add a drop of a solution 

 of iodine in iodide of potassium, and examine with the microscope. 

 A thin section of large leaves may be examined in this manner. 



EXPERIMENT 49. 



STARCH AS AN INDICATION OF PHOTOSYNTHESIS. 



Place some Spirogyra or Vaucheria in a dark chamber for 24 

 hours. Test some of the filaments for starch. It will be found 

 absent. Set the vessel containing the filaments in the sunlight for 

 a few minutes. Examine a second lot. Starch will be found 

 present. 



EXPERIMENT 50. 



FORMATION OF STARCH FROM SUGAR. 



Deprive a Geranium plant of starch by placing in a dark cham- 

 ber for 24 hours or longer. Test for starch, and if none is present 

 cut off a leaf and place it in a 20^ solution of sugar for a week in a 

 dark chamber. Test for starch. The protoplasm of the leaf has 

 used the sugar as food and has also converted a portion of it into 

 starch. 



