CHAPTER X 



POLLINATION AND FERTILIZATION 



124. Pollination. In the great majority of flowering plants 

 seed production depends indirectly upon pollen. Of course the 

 pollen grain, in order to act, must be transferred from the anther, 

 where it was formed, to the pistil, in which are the ovules to 



be affected. This transference of 

 pollen is called pollination. 



In the higher seed plants the 

 pollen is received on the surface of 

 the stigma, which is usually rough, 

 moist, and sticky, and therefore 

 readily retains the grains which 

 reach its surface. The details of 

 the pollinating process differ so 

 much in different kinds of flowers 

 that even a mere statement of the 

 various types requires considerable 

 space. The significance of pollina- 

 tion will appear more clearly if 

 we first give a very brief account 

 of the results of pollination, and 

 then consider a few of the modes 

 of transference of pollen. 



125. Pollen grains ; formation of pollen tubes. The form of 

 pollen grain for any given kind of flower, as a lily, a hollyhock, 

 or a cucumber blossom, is quite constant, but those of differ- 

 ent kinds are so often unlike that the whole number of forms 

 observed is very great. Usually the grains are separate, like 

 those shown in figure 117, but in many kinds they are united by 



134 



FIG. 117. Types of pollen grains 



A, dandelion ; B, hemp ; C, gen- 

 tian; D, squash. All greatly 

 magnified. After Kerner 



