THE LEAVES 



71 



the vein-plan is not disturbed. Now, owing to the long 

 life of a gum tree leaf, it is often broken at the edge 

 or bitten by insects. Look at a number of fallen gum 

 tree leaves, and you will see that the insect often 

 stops at the edge-vein. If you have ever reared moths 

 you will have noticed that small caterpillars often avoid 

 veins in the leaves they eat. 



7. How the leaf-sap returns to the stem. You 

 have often watched, on the playground, how little 

 streams of rain gather into larger streams, and these 

 into still larger till the gutter is reached. In a similar 

 way, the sap that has flowed over the leaf flows back 



into the veins and the ribs 

 and the stalk and, at last, 

 into the stem. The root- 

 sap has now been mixed 

 with the air-food caught by 

 the leaf, and is therefore 

 no longer root-sap. It is 

 now leaf-sap ; and it is 

 ready to build up wood and 

 bark, bud and root. It no 

 longer flows in the new 

 wood, but down the inner 

 bark. 



8. The shapes of leaves. 

 And now we are ready to 

 think about the different 

 vein plans in different kinds 

 of leaves. Walk through a 

 large garden, and look at 

 nothing else but the shapes 

 of the leaves and the plans 



F 



Fl(r 123 



Edge-vein of gum tree leaf. 



