THE LIVING PLANT 37 



EXERCISE VI. Exercises in plasmolysis and turgidity. 



1. Explain and illustrate with drawings plasmolysis of a cell. 



2. Materials. Stems of various plants such as geranium, alfalfa, 

 marguerite, grape, cactus, peach twig, olive or oleander twig, pine 

 twig. 



Procedure. Allow the stems to wilt for various lengths of time and 

 then place them in water. What is the cause of the wilting? To 

 what extent is it possible to let the stems wilt and have them recover? 

 Does wilting injure all plants to the same extent? What effect has 

 wilting on cuttings or young trees to be planted? 



EXERCISE VII. Experiment illustrating the ascent of water in 

 plants. 



Materials. Fresh growing stems of willow or orange; eosin solution. 



Procedure. Place the stem in dilute eosin solution with the cut end 

 downward. After a time trace the upward path of the water by the 

 red color. What part of the stem carries the water upward? What 

 effect would the girdling of the bark of a tree have on the upward 

 passage of water? 



EXERCISE VIII. Experiment to illustrate transpiration 



Materials. Two tumblers; cardboard; geranium or other leaf. 



Procedure. Nearly fill a tumbler with water. Punch a hole in the 

 center of a piece of cardboard and put the petiole of a leaf through the 

 hole. Place the cardboard on top of the tumbler so that one end of 

 the petiole projects into the water. Place a dry tumbler inverted upon 

 the cardboard so as to cover the blade of the leaf. Notice the drops 

 of moisture that gather after a few hours on the inner surface of the 

 upper tumbler. Where did this water come from? Through what 

 part of the leaf must the water pass in order to get to the blade? At 

 what points does the moisture get out of the leaf into the air? 



EXERCISE IX. Experiment to locate stomata. 



Materials. Twigs with their leaves; boiling water. 

 Procedure. Heat some water to boiling and plunge the end of a 

 twig into it. Notice the forming of gas bubbles at the stomata. 



EXERCISE X. Experiment to show that carbon dioxide is given off 

 by plants. 



Materials. Leaves of clover, alfalfa, or other plants; small vial; 

 lime-water; air-tight jar. 



