THE LEAVES 



m 



for a true leaf. Compare it with a gum tree leaf, and 

 you will see, at once, that it is not an ordinary leaf. 



Look carefully also at a 

 full-grown blackwood 

 tree, and you will some- 

 times see, even among 

 the higher branches, a 

 leaf-stalk with the true 

 acacia leaflets on it. 

 This shews, does it not, 

 that what looks like a leaf 

 is really a leaf-stalk ? 



12. How sap-flow 

 shapes the leaf. Can 

 you guess why the 

 higher leaves of the ivy 

 (fig. 59) are quite dif- 

 ferent in shape from the 

 ordinary leaves (iig. 

 60) ? Why is the lower 

 leaf lobed while the 

 upper leaf is entire ? If you watch the growth of an 

 ivy plant, you will find that it is when the growth is 



Blackwood CLightwoot^). The lowest 

 branch shows the usual acacia leaf- 

 lets; the middle branch shows the leaf 

 .stalk beginning to flatten ; the third 

 branch shows the flattened leaf stalk 

 taking the place of a leaf. 



Fig. 69. 



Upper leaf of Ivy (an 



entire leaf). 



Lower leaf of ivy. 



