86 HOW ARE ANIMALS AND PLANTS DEPENDENT? 



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Pollen grains may take 

 various forms. What might 

 be the value of the spine- 

 Explain, with reference to your text, the stages in the like structures on the pollen 

 germination of a pollen grain. grains ? 



forms an embryo or baby plant. This is contained in the seed 



and, as we know, will develop into an adult plant if given proper 



environmental conditions. 



Practical Exercise 9. Make a series of diagrams to show just how the 

 sperm nucleus reaches the egg cell in order to bring about fertilization. 

 Make an enlarged diagram to show how fertilization takes place. 



Self-Testing Exercise 



The parts of a flower are (1), (2), (3), 



(4), and (5). Essential organs are the (6) 



and the (7). Pollen is produced in the (8). Egg 



cells are found in the (9). Fertilization of the (10) 



by a (11) nucleus from the pollen (12) causes 



an (13) or (14) plant to be formed. 



PROBLEM VIII. HOW ARE FRUITS FORMED? 



Laboratory Exercise. Examine an unopened pea or bean pod. 

 Compare it with a pea or bean flower or with drawing. Find the 

 parts of the flower in the fruit. What becomes of the petals and se- 

 pals? What happens to the pistil? Where do the seeds grow? 



The pod of a bean, pea, or locust illustrates well the growth 

 from the flower. The flower stalk, the ovary, and the remains 

 of the style, the stigma, and the calyx, can be found on most 



