NATURE-STUDY LESSONS. 117 



7. In house plants, shrubs and trees, observe what 

 position the leaves generally take relative to sunlight. 



8. From observations of the position, color and form 

 of leaves, infer one essential condition of their healthful 

 activity. 



9. {a) Examine a spray of the maple. 



(<5) Compare the different leaves on the spray as to ; 

 (i) Shape. 



(2) Size. 



(3) Length of petiole. 



10. Supposing all the leaves on this spray were of the 

 same size and with petioles of equal length, how would 

 the amount of sunlight received by some of them be 

 affected ? 



11. Assuming sunlight to be necessary to the life of 

 the leaf, account for the varying sizes of the blade and 

 the difference in length of the petioles. 



1 2. (a) Examine the leaves of a house plant, as a geran- 



ium or shamrock, grown in window light. 

 (p) What is their position relative to the sunlight 



entering the window? 

 {c) Turn the pot around and after some days note 



any change in the position of the leaves. 

 (d) Infer the cause of this change of position. 



B. The Life-Work of the Leaf, 



1 3. {a) Place a vigorous leaf (freshly cut) so that its 



petiole may pierce a piece of cardboard and 

 enter water contained in a tumbler. Cover 

 the blade with another tumbler inverted and 

 resting on the cardboard. After some time 

 examine the inner surface of the upper tum- 

 bler. 



