PROBLEM 13 



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enlarged part at the base (not always easily seen) is the ovary; 

 the stalk is the style; the tip, which is sticky, is called the stigma. 

 On this sticky surface pollen grains will grow. How might pollen 

 get to the stigma? 



Cut a cross section through the ovary. Describe what you find 

 inside. These little 

 structures are caUed 

 ovules. Under cer- 

 tain conditions, which 

 we will later discuss, 

 a part of a pollen 

 grain will cause these 

 ovules to grow into 



Fill out a diagram 

 like the accompany- 

 ing in your notebook. 



Conclusion. 1. What parts of the flower are essential for the 

 production of seeds? 



2. What are then the essential organs of a flower? 



Drawings. 1. A flower from above. Label all parts. 



2. A stamen, showing all parts. 



3. A pistil, showing all parts. 



Problem 13 : The cross-pollination of flowers. 



Method. Take a trip to a locality where flowers are abundant 

 and make a preliminary study of the relation of insects to flowers. 



Observations. Notice whether the flowers are being visited 

 by insects. 



To what orders do these insects belong? 



Do bees visit flowers of one sort in succession, or of different 

 sorts? Make a careful study of this point by following a single 

 bee or other insect. Work this out in the case of a butterfly. 



Do insects seem to prefer any one color in flowers to another 

 color? Make careful observations on this point. 



Can you discover any means by which the flower might attract 

 an insect? Remember insects can probably smell and taste as 



