Suggestions for Laboratory Work to Precede Chapter Five 



1. Cut a leaf from some plant, preferably under water. Then 

 immerse the cut end in red ink or eosin and let it stand for some 

 time, watching the movement of the red color in the veins. Thin 

 leaves,, like those of balsam and nasturtium, are especially suited 

 to this experiment. If thick leaves are used, they may be spUt 

 with a knife in order to show the veins. 



2. Study the surface coverings — cuticle, wax, and hairs — on 

 a series of leaves like the mullein, century plant, bur oak, tomato, 

 and geranium. 



3. Compare leaves of water plants and moist soil plants with 

 those of desert forms like the yucca, agave, and cactus. 



4. Examine free-hand sections of leaves or prepared microscope 

 slides that will show variations in stomata, compactness of tissue, 

 development of air chambers, and water storage. 



5. Determine the relative time required for the wilting and 

 complete drying out of several kinds of leaves, using leaves of 

 different texture, thickness, and surface covering. 



6. Take three similar leaves from a single plant. Cover with a 

 thin layer of vaselin the upper surface of one, the lower surface of 

 another, and both surfaces of the third. Determine the relative 

 time required for the leaves to wilt and also to dry out completely. 



7. Experiments : 



Show that water is given off by plants, by covering a plant with 

 a bell jar. 



Ascertain the amount of water transpired by a potted plant, by 

 covering the pot and soU with melted paraffin and weighing the 

 plant at intervals. 



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