CHAPTER XVIII. 

 METHODS OF POLLINATION. 



278. The necessity of pollination. Pollination is the trans- 

 ference of the pollen from the anthers to the stigma of the pistil. 

 This is necessary in order that the pollen grain may germinate, 



Fig. 127. 

 Photomicrograph of pollen grains of sunflower, highly magnified. 



and that the pollen tube, by making its way down through the 

 style, may reach and enter the ovule, to carry the sperm cell 

 (the fertilizing element) to the egg cell. The union of the sperm 

 cell and egg cell brings about the fertilization of the egg cell, 

 which is necessary (except in rare cases) in order that the egg 

 may develop into the embryo and bring about the formation of 

 the seed. There are many different devices, or mechanisms, in 

 the flower structure for bringing about pollination.* 

 * See Darwin, Cross fertilization, etc. 



167 v 



