HOW PLANTS GROW 351 



are grown by planting healthy seeds from fruits with 

 seeds. 



In the case of the banana, however, the disintegration 

 of the embryo sacs has become such a fixed habit that 

 seeds are never found in cultivated varieties. Pineapple 

 plants are propagated by cuttings, and only very rarely 

 can a seed be found in a pineapple. These cuttings are 

 shoots or " suckers" which spring up from the base of 

 the old plants. These new cuttings bear fruit after from 

 fourteen to eighteen months. A pineapple plant grown 

 from seed does not grow fruit until after it is ten or 

 twelve years old. 



QUESTIONS AND EXERCISES 



1. What is the difference between beans and corn on the 

 bases of appearance and structure? 



2. What nutrients do beans and cereal grains contain? Why 

 are such plants grown? 



3. Explain the process of germination of seeds. 



4. What are the necessary conditions for the growth of 

 healthy plants from seeds? 



5. In what direction do roots grow? Why? Of what use 

 are roots to plants? 



6. What are the conditions for osmosis to take place? Does 

 osmosis occur in your body? 



7. Does the root or stem grow first from a germinating seed? 

 What are the parts of the stem of a plant? Give the use of 

 each part. 



8. What are the parts of a leaf? Give the use of each part. 



9. Is it better for trees to have the leaves fall off every year? 

 Explain. 



10. Why do plants grow flowers? Name the parts of a 

 flower. Give the use of each part. 



11. How are new varieties of plants produced? 



12. How are seedless oranges grown? 



