46 Plants and their Ways in South Africa 





much to call a leaf. In the bean we called what looked like 

 three leaves a single leaf. How shall we tell that the third 

 leaf in the bean was not three leaves? In studying branches, 

 we found that they were borne in the axil of each leaf. If you 

 examine a branch with leaves like those in Fig. 51, will 

 you find buds at the base of each part or only where the main 

 stalk joins the stem ? 



Another test will help us to decide. Leaves remain on a 

 tree for a certain length of time and then fall. When a leaf 

 like that in Fig. 5 1 falls, does the stalk that extends through 

 the centre remain or fall off too ? A leaf that has several dis- 

 tinct parts or leaflets is a compound leaf. 



The Parts of a Leaf. Fig. 5 2 is the leaf of Hibiscus. It 

 has one large flat upper portion, the blade, a stalk or petiole, 

 and at the base two small leaf-like 

 bodies called stipules. If a leaf has 

 no stipules it is said to be exstip- 

 ulate. If the leaf-blade joins directly 

 upon the stem and has no stalk, it is 

 sessile. The needle-shaped leaves 

 of pines and heaths have no expanded 

 blades. Sometimes stipules are de- 

 ciduous ; that is, they fall off very 

 quickly, as the Fig and Oak. We 

 must examine young leaves to make 

 sure whether they are stipulate or ex- 

 stipulate. 



The Veins of a Leaf. Hold a 

 thin leaf up to the light and notice 

 how it is marked with delicate veins. 

 These are made up of the long hollow 

 tubes which carry the food material to its destination. They 

 also serve as a framework to prevent the leaf from tearing. Do 

 they serve like the framework of an umbrella to keep the leaf 

 sprea'd out ? You can answer this by looking at pumpkin leaves 

 which have withered in the heat on a sunny day. 



The species* of Senetio (Fig. 53) has a thick leaf stored with 

 food, which would be wasted if the leaf were torn in the 



FIG. 52. Simple leaf of 

 Hibiscus with stipules. 



