THE LEAF 99 



there some hours. The starch does not disappear. In 

 other words it is insoluble in the water. Put a lump of 

 sugar in water. It quickly disappears, being soluble in 

 water. Starch, then, is insoluble in water, whilst sugar is 

 soluble. Soluble substances can readily pass from one 

 part of a plant to another. If now we can show that 

 starch is changed in the leaf to sugar, we can easily 

 understand how it may be that a leaf containing starch 

 in the afternoon may have none in the morning. It may, 

 in fact, have been altered into sugar and carried away to 

 other parts of the plant. A convenient method of test- 

 ing sugar is by adding some to a solution known as 

 Fehling's solution, and boiling for a minute in a test- 

 tube. When this is done a red deposit or precipitate 

 collects in the bottom of the tube, whilst with starch no 

 red precipitate is formed. 



Take two test-tubes, and fill each about one-quarter 

 full of Fehling's solution. To one add a very little starch, 

 and to the second add a few drops of honey. Boil both. 

 In the second a red precipitate collects, whilst no red 

 precipitate is formed in the first. 



Take a little starch on the end of a penknife, mix it 

 up with some cold water, and drop it into about half a 

 pint of boiling water, and boil for two minutes. When 

 cool, add iodine to a small portion. It turns blue, show- 

 ing the presence of starch. To a second small portion 

 add Fehling's solution, and boil for not more than a 

 minute. No red precipitate forms, showing that no 

 sugar is present 



Place in two fresh test-tubes some more of the starch 

 in water, and add to each some saliva, and put the two 



