PROBLEM 2. The Part Stems and Roots Play in Makmg Food 165 



3. Report on the economic importance of roots. 



4. It would be interesting to see whether the amount of moisture af- 

 fects the development of root hairs. Raise germinated oat or mustard 

 seeds under different moisture conditions under glass. 



5. You could show the class the result of sprinkling salt or too much 

 fertilizer on the soil in a pot of growing seedlings. (Plant 20 or 30 lentils. 

 Let them grow until they are two or three inches tall.) Could you set up 

 an experiment with a thistle tube to explain what happens? 



6. Are epidermal cells completely waterproof? Some leaves, such as 

 apple and barberry, have no stomata on the upper surface. Find out 

 whether any transpiration goes on. (Cobalt paper turns red when moist.) 



7. Does light affect the rate of transpiration? Can you devise an ex- 

 periment to find the answer? 



8. If willow twigs are available you can make a whistle and find out 

 at the same time where the cambium lies. Gently pound a short piece of 

 stem all around. Thus you can separate the wood from the bark and 

 remove it. 



hi UNIT IV you will consider these problems: 



Problem i . How Can We Choose Foods Wisely? 



Problem 2. How Does the Digestive System Make Foods 

 Usable? 



Problem 3. How Are Materials Moved to and from Our Body 

 Cells? 



Problem 4. How Are All Our Cells Provided with a Constant 

 Supply of Oxygen? 



Problem 5. How Does the Body Get Rid of Wastes Formed 

 by Cell Activity? 



Problem 6. What Substances Help Regulate Cell Activities? 



