94 CIRCULATION AND USES OF FOOD BY PLANTS 



Problem 78: To find out through which part of a woody 

 stem food passes down. 



Materials. — Growing willow twigs, nutrient solution, or water. 

 Upper figure page 100, Civic Biology. 



N. B. — This experiment should be started at least three weeks before it is to be 

 used. 



Method. — Allow willow twigs to grow in water until they have 

 formed roots, then girdle them by removing a strip of bark 

 about half an inch wide and about an inch above the cut end of 

 the twig. Replace the twigs in water. 



Observations. — After several days notice what has happened 

 both above and below the girdled area. 



Conclusion. — 1. Through which part of the stem does food 

 get to the roots? How do you know? 



2. Write a paragraph telling how water rises and food materials 

 pass through a woody stem, giving reasons from this and other 

 experiments. 



Drawing. — Illustrate your experiment with drawings before 

 and after girdling. The teacher should at this point recall the 

 experiment to show the condition of the food in the stem or root 

 when it passes up or down through the fibro vascular bundles. 



Problem 79 : How plants with special digestive organs get 

 their nitrogenous food. 



Materials. — Specimens of pitcher plant, sundew, Venus's-fly- 

 trap, and charts to illustrate. Figures page 102, Civic Biology. 



Observations. — Look carefully within the pitcherlike leaves of 

 the pitcher plant. What do you find ? With the aid of the chart 

 work out exactly how the sundew and Venus's-flytrap catch 

 insects. 



Conclusion. — What do the above plants do with the dead 

 insects ? 



Problem Questions 



1. Of what use to a plant is each part of a woody stem ? 



2. In what condition must food be to pass through a stem? 

 How do you know ? 



