THE STRUCTURE OF A LEAF 



Practical Exercise 4. Fill out the following : 



151 



Types of Roots 



Functions 



Adaptations 



Examples 











Self-Testing Exercise 



Roots act as (1) and absorb (2) as well as 



(3) . Some roots store (4) . Plants may (5) by- 

 means of (6). Many plants produce (7) wherever 



the (8) happens to (9) the ground (10) 



plants absorb food from the (11) on which they (12). 



PROBLEM VI. WHERE DOES THE GREEN PLANT 

 MANUFACTURE FOOD? 



The primary function of the green leaf is the manufacture of 

 food from the raw materials which are absorbed through the cell 

 walls. 



Laboratory Exercise. Examine a leaf of maple or oak. Notice 

 that it consists of two parts : a stem, the petiole, and a broad expanded 

 part, the blade. Note, also, that the petiole leads into a number of 

 branching veins which support the blade. Notice the arrangement 

 of leaves. Can they all receive full sunlight? Estimate the amount 

 of green leaf surface in a plant in the room by multiplying the surface 

 area of one leaf by the number of leaves on the plant. Place in red ink 

 the cut end of a growing shoot from a young tree or shrub. Leave for 

 24 hours. What happens? 



State uses of the veins. Explain how the leaf is fitted to receive light. 



The structure of a leaf. In the experiment with the red ink 

 and young shoots we shall find that the fluid has gone into the 

 skeleton or framework of the leaf. Let us examine a simple leaf 

 more Carefully. It shows usually (1) a flat, broad blade, which 

 may take almost any conceivable shape ; (2) a stalk, or petiole, 

 which spreads out into veins in the blade ; (3) stipules, a pair of 



