334 GENERAL SCIENCE 



growth of certain plants. The region may be too cold, too 

 hot, too wet, or too dry for the development of a certain 

 plant. Some of our common grains cannot grow in the 

 dry soil of the southwestern states where the giant cactus 

 thrives. In the frigid zone, only mosses and lichens grow. 

 From the Arctic circle to the equator the vegetation differs 

 widely. In the colder part of the temperate zone, cone- 

 bearing evergreen trees are found. Farther south, in 

 the same zone, are deciduous trees such as the beech, 

 maple, oak, and chestnut ; while in the tropics are found 

 the mahogany, cypress, and many varieties of palms. 



QUESTIONS 



1. Why is food essential to living matter? 



2. When a plant is placed in water it will live for a while. What 

 determines the length of time it will live ? 



3. Why do seeds not germinate if the ground is too wet? 



4. What are the conditions necessary for seed germination? 



5. Is light necessary for germination? 



6. Name some plants whose seeds are dispersed by winds. 

 By animals. 



7. Which develops first, the root or the stem of a plant? 



8. Why do roots grow down? 



9. Name three commercial uses of bark. 



10. What is meant by " quarter-sawing? " 



11. From where does the water come that is evaporated from 

 the leaves? 



12. Is it essential that a plant lose water by evaporation from 

 its leaves? 



13. Name three functions of leaves. 



14. Is there any starch in toadstools and mushrooms? Why? 



15. Potato sprouts which grow in a dark cellar are white. Why? 



16. When are molds and yeasts harmful? 



17. How do yeast plants cause bread to rise? 



18. How do plants prepare food? From what materials? 



19. What is the effect of cultivation on plants? 



