102 PHYSIOLOGICAL PROCESSES IN PLANTS 



4. If evaporation of water is a cooling process, what is the effect pro- 

 duced on the climate by a large number of leafy trees ? 



5. Where would there likely be the most rainfall, over forest areas 

 or over areas where there are no trees ? Explain. 



6. Give an argument for the preservation of our forests. 



7. Trace the ow of water in a plant from its absorption by osmosis in 

 the root hairs, until it is either used in photosynthesis or transpired. 



4. THE LEAF AS A MILL (OPTIONAL) 



Conclusions. 1. If the sun furnishes the energy to run the mill and 

 the chlorophyll grains are the millstones, and the leaf the mill, and " air 

 food" (carbon" dioxide) and the "soil food" (soil water) are the raw 

 products put into the mill, what is the manufactured product ? The by- 

 products ? 



2. Kefer to Figure 27 and see if you can explain just where all the 

 substances mentioned come from, and what becomes of them. 



3. What are represented by the two lower tubes ? Where does the 

 incoming tube originate and what does it bring ? What does the outgoing 

 tube take away ? In what condition, or what substance is it ? 



4. Just where have you already found these tubes located in the stem ? 



5. Try comparing the business of a leaf with the business of a factory, 

 using such terms as "machinery," "raw materials," "manufactured 

 products," "by-products," "wastes," "market," "transportation to 

 market," etc. 



d. Means of Protection (Optional) 

 1. AGAIXST ANIMALS 



Fill in the above table with as many plants as you can that have 

 leaves that protect themselves as indicated at the tops of the columns. 

 Write a paragraph, summing up the information tabulated. 



