CHAPTER VIII 

 HOW GREEN PLANTS MAKE FOOD 



Problems: To study the structure of a leaf in order to find out how 

 moisture is given off. 



To find the reaction of leaves to light. 



To study photosynthesis : the conditions and materials necessary, 

 and the hy -product. 



To learn what other functions are performed hy leaves. 



Laboratory Suggestions 



Demonstration. The passage of fluids up the stem. 



Demonstration. Water vapor given off by a plant in sunHght. Loss of 

 weight due to transpiration measured. 

 Laboratory exercise. 



(a) Gross structure of a leaf. 



(6) Study of stomata and lower epidermis under microscope. 



(c) Study of cross section to show cells and air spaces. 

 Demonstration. Reaction of leaves to light. 

 Demonstration. Light necessary in starch making. 

 Demonstration. Chlorophyll necessary in starch making. 

 Demonstration. Air necessary in starch making. 

 Demonstration. Oxygen a by-product of starch making. 



What becomes of the Water taken in by the Roots ? — We have 

 seen that more than pure water is absorbed through the root hairs 

 into the roots. What becomes of this water and the other sub- 

 stances that have been absorbed? This question may be partly 

 answered by the following experiments. 



Passage of Fluids up the Stem. — If young growing shoots 

 from bean or pea seedlings are placed in red ink (eosin) and left 

 in the sun for a few hours, some of the red ink will be found to 

 have passed up the stem. 



Water given off by Evaporation from Leaves. — Take some well- 

 watered potted green plant, as a geranium or hydrangea, cover the 

 pot with sheet rubber, fastening the rubber close to the stem of 

 the plant. Next weigh the plant with the pot. Then cover it 

 with a tall bell jar and place the apparatus in the sun. Id a short 



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