44 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. 51 falls, does the stalk that extends through 

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

 distinct parts or leaflets is a compound leaf. 



The Parts of a Leaf. — Fig. 52 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 

 exstipulate. 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 deciduous ; 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 

 exstipulate. 



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 sap 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 

 spread out? You can answer this by looking at pumpkin 

 leaves which have withered in the heat on a sunny day. 



Senecio has a thick leaf stored with food, which would be 

 wasted if the leaf were torn in the wind. It has a firm vein 



Fig. 52. — Simple leaf of Hibis- 

 cus with stipules. 



