84. Sugar and starch in the leaf. Sugar is commonly formed 

 in the leaf in the process of photosynthesis, and it is being 

 continually carried away for use in other parts of the plant. 

 On a bright, sunny day it is made much more rapidly than it 

 can be carried away or used, and if there were not some way 

 to dispose of it, 

 the sugar would 

 accumulate in the 

 leaf until the sap 

 became so filled 

 with it that the 

 work of the leaf 

 could not go on. 

 The leaf has the 

 power of changing 

 the excess sugar 

 into starch. This 

 removes the ex- 

 cess carbohydrate 

 from the sap, since 

 starch is not read- 

 ily dissolved in 

 water. It is possi- 

 ble that when the 

 leaf is working 

 rapidly, instead of 

 forming sugar and 

 changing it into 



FIG. 41. Dodder, a dependent plant 



The tangled, leafless vine is the dodder. It secures 



its food from the other plant, which is known as its 



host, while the dodder is a parasite 



starch, the leaf may form starch directly from the simpler 

 compounds. At any rate, by evening, if the day has been a 

 bright one, a great deal of starch is stored in the leaf. At 

 night, when no sugar is being made, the starch in the leaf is 

 slowly changed into sugar and carried away, and by morning 

 little starch remains in the leaf. The process of changing 

 sugar into starch or starch into sugar does not require light. 



