120 NATURE-STUDY LESSONS. 



26. From these facts, infer the effect of growing-plants 

 upon the air of a room. 



The advanced class may continue experiments witli a view to demon- 

 strate that growing-plants are healthful in living-rooms during daylight, but 

 injurious at night. 



27. What three facts have been learned about the work 

 of the leaf? 



C. Relation between the Leaf and the Boot. 



28. Examine the position of the leaves of the turnip, 

 beet, radish and rhubarb. 



29. {a) What is the course of the collected rain-drops 



or the triclcling dew on the surface of these 

 leaves ? 



(b) What relation do the creases in these leaf' 



blades bear to this course of the water? 



30. (fl) Now, examine the roots of these plants. 

 {b) What course do they take in their growth ? 

 {c) Infer a reason for this. 



31. («) Examine the relative position of the apex and 



base of the leaves on maples, elms and wil- 

 lows. 

 (J>) Generally, which is on the higher level ? 



(c) Infer the course taken by rain-water on such 



trees. 



32. {a) Examine the roots of these trees and state the 



direction of their growth. 

 (b) Infer why their development should be lateral 

 rather than vertically downward, and where 

 a fertilizer should be placed intended to 

 reach the roots of a large tree. 



33. From these observations, what general conclusion 

 can be drawn with reference to the relation between the 

 position of the leaf and the direction of the development 

 of the roots ? 



