CHAPTER XXII 



POLLINATION AND SEED FORMING 



Problem. — What is the work o] a flower? What is 

 pollination and how is it secured by dijjerent flowers ? 



For this study any flower in which all the parts are well 

 represented should be selected. Petunia, nasturtium, 

 morning-glory, and tomato are all good. It is well to 

 study more than one flower. 



Find the parts of the flower: (a) corolla, composed of 

 petals, the colored showy part, called polypetalous when 

 the petals are separate as in the nasturtium, sympetalous 

 when the petals are grown together as in the petunia; (b) 

 calyx, composed of sepals, sometimes green, as in the 

 petunia, sometimes colored, as in the nasturtium. 



Find the stamens. How many? Note the slender 

 filaments and the knoblike anther. Can you find any 

 powder (pollen) in the anther? Compare anthers in old 

 flowers with those newly opened. What has happened in 

 the older ones ? Examine the pistil. Make out the ovary 

 at the base, the style, and the stigma at the top. What is 

 the use of the stigma ? This is to catch the pollen. When 

 it is ripe, or just ready to catch pollen, it is sticky. When- 

 ever pollen is transferred from an anther to a stigma 

 pollination has taken place. Pollination then is the trans- 

 fer of pollen from anther to stigma and nothing more. It 

 should not be confused with the subsequent and entirely 



