EXERCISE 28 



WHAT USE MAY THE PLANT MAKE OF FOOD MATERIALS, 

 SUCH AS STARCH? 



Materials. Pieces of green willow about twelve inches long and 

 one-half or three-eighths inch in diameter ; quart fruit jar. 



Directions for work. Stand the . willow branches in the jar in 

 about four inches of water. Place the jar in a sunny window. 

 When roots are beginning to break through the bark near the 

 lower end of the sticks, girdle all of them excepting one by 

 removing a narrow strip of bark all around the stick. Be sure 

 to remove the bark clear to the wood. Some of the pieces may 

 be girdled just above the water level and others at or below 

 the surface of the water. 



Watch the further growth of roots above and below the girdle 

 and compare with the uninjured branch. What effect upon the 

 growth of the roots results from interruption of the bark ? On 

 the supposition that the bark is the principal path for the trans- 

 fer of food, what use does the plant appear to be making of 

 food stored in the stem or manufactured by the leaves ? To 

 what other similar purposes may food possibly be put in the 

 plant ? 



References 



BERGEN and CALDWELL. Practical Botany, pp. 77-81. 

 BERGEN and CALDWELL. Introduction to Botany, pp. 43-46. 



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