WHERE FOOD COMES FROM 125 



11. How does a leaf get carbon dioxid to its chlorophyl cells? water? 



12. What parts of a leaf are not directly concerned with food-making ? 

 What relation have these parts to the life of the plant? 



13. How is the root of a plant related to food-making ? 



14. How does a root grow in length ? in thickness ? What is the source 

 of the grow- th material ? 



15. How is the stem of a plant related to food-making ? 



16. How does a stem grow in length ? in thickness ? What is the 

 source of its growth material ? 



17. What use can we make of the fact that chlorophyl disappears from 

 plant cells in darkness ? 



18. What use can we make of the fact that chlorophyl transforms light 

 into heat that may "scorch" the leaf? 



19. What use can we make of the fact that plants accumulate surplus 

 food in leaf, in stem, or in root ? 



20. What use can we make of the fact that various parts of a plant 

 may replace missing organs and form a complete plant ? 



21. What use can we make of the fact that, in spreading out toward 

 the light and air, plants develop various mechanical structures ? 



22. What use can we make of the fact that in the course of their 

 activities plants produce a variety of substances that are neither nutri- 

 ents nor mechanical supports nor protection ? 



23. How can we tell that living leaves give off water ? 



24. How can we tell that matter from the soil travels through a plant 

 along different channels from those followed by food sap? 



REFERENCE READINGS 



Bergen and Caldwell. Practical Botany, pp. 15-20. 55-71. 



OsTERHOUT, W. J. V. Experiments with Plants, pp. 180-203; chap, v, 

 The Work of Stems. 



Densmore, H. D. General Botany, chap, vi. The Structure and Func- 

 tions of Stems, Roots, and Leaves; pp. 11 7-1 24, 142-146. 



Gave, Selina. Why Plants need Water (extract in C^H Ward's ''Ex- 

 ploring Nature," pp. 69-74). /\ f^BO/?^ 



