THE PLANT 



49 



through the wood, is changed to food in the leaves, and feeds the 

 upper part of the plant. But it cannot go below the girdled cam- 

 bium to feed the roots. Sooner or later in the case of a tree 

 it may be several months the roots die of starvation. A farmer 

 often girdles in summer trees that he wishes to kill; they die 

 entirely, root first. If they were cut down, the roots might still 

 live and send up new growth year after year. 



AN EAR OF CORN, THE 'SILK' OF WHICH WAS NOT FERTILIZED KY POLLEN 

 FROM THE TASSELS OF ANOTHER PLANT 



Leaves. You have learned that leaves are formed of clear 

 cells containing a green coloring matter called chlorophyl, and that 

 they manufacture food for the plants. Therefore you realize that 

 the presence and health of the foliage are very important. If it 

 be destroyed, as by disease, the whole plant will suffer and 

 perhaps die. If crops are shaded by trees or weeds, the manu- 

 facture of plant food in the leaves* is hindered for lack of sun- 

 light. 



Sugar and starch are stored up in some leaves, as they are 

 in some roots. It is this store which makes the leaves of cabbage 

 valuable for food. 



Underground Leaves. There are underground leaves as well 

 as underground stems. They are never green in color, because 



