HOW THE PLANT USES THE FOOD IT MAKES 87 



How are the new parts formed in the bud? Get 



some heads of cabbage or Brussels sprouts. These are 

 merely large buds. Cut them open and find the tiniest 

 leaves as they are forming at the tip of the stem. No- 

 tice how new buds are formed just where the leaf is 

 attached to the stem. Test these and other buds for 

 food (see page 83). Certain animals live partly on 

 buds in winter. Why do the buds have so much food 

 in them? 



How stems grow in thickness. We all know that 

 just outside the wood of a tree there is a soft juicy layer 

 which is protected by the bark which covers it. This is 

 the place where growth in thickness takes place. It is 

 called the cambium. It makes new wood arid new bark 

 all the time during the growing season. 



When we cut off a limb, the cambium grows out and 

 covers the cut surface (figure 45) , so as to keep the wood 

 from rotting. If we paint the cut surface with tar 

 every little while, we can keep the wood sound until the 

 cambium can cover it. Always cut off a limb close to 

 the trunk; then the cambium will cover it much better 

 than if a large stub is left sticking out from the trunk 

 (figures 46 and 47). 



The cambium makes scion and stock grow together iri 

 grafting. No matter what method of grafting be used, 

 the cambium of the scion must be placed so that it 

 presses against the cambium of the stock. There the 

 two grow together and the graft is a success. 



