152 



LEAVES 



FIG. 63. 



tube with water which has been dis- 

 tilled or boiled to expel any air. Stand 

 the tube over the beaker of mercury as 

 shown in Figure 63. 



After a few hours note what has oc- 

 curred. How do you account for the 

 result ? 



Conclusion. Your inference from this. 



Note. The effect of light on the root was 

 shown in Experiment 94 and its influence 

 on stems was seen in Experiments 103 and 

 104. We will now make similar experiments 

 and see how light acts on leaves. 



133. LEAVES 



Object. To discover the effect of light 

 upon foliage. 



Apparatus. The dark box used in Experiment 51, also another 

 similar box having a small hole or window with an interior cut-off 

 so arranged as to prevent the direct rays from reaching the plant 

 within. Plant some young vigorous seedlings in small pots. 



Method. Place a plant in each dark box and also one 

 outside where it will receive plenty of light. Let them remain 

 for several days and then compare them. 



Observe the following: 



(1) Color of each plant. 



(2) Vigor or weakness of its growth as compared with 

 the others. 



(3) Position of the plant in the box. 



(4) Size of the leaves. 



(5) Length of the internodes. 



Conclusion. What may be inferred regarding the effect 

 of light on foliage ? 



