148 The Great World's Farm 



4. For what does the plant need carbon? 



5. How is carbon supplied to the air? 



6. What gases make up the air? 



7. Illustrate the fact that gases will mix, whatever their 

 weight. 



8. What fact, regarding carbon dioxide, does this explain? 



9. What important share has carbon in the structure of 

 plants? 



10. Describe the two sets of cells in a leaf. 



11. What happens in the "leaf-green" cells? 



12. What two things are necessary to the supply of leaf- 

 green? 



13. How is the plant dependent upon the sun? 



14. How do plants which have no leaf-green secure their 

 food? 



15. How do seeds and bulbs grow without leaf-green? 



16. Describe the breathing of plants and of blossoms? 



