96 



PHYSIOLOGY 



The stamen is a long filament with an anther at the top. 

 The anther gives rise to the pollen grains. These grains 

 are so tiny that they are easily blown about by the wind 



Fig. 53.— Flower showing stamens and pistil. 



to fall perhaps on the sticky surface of the stigma. 

 Each little pollen grain may be compared to the male 

 sea-urchin, for it forms within itself a sperm cell. 



The sperm cell, like that of the sea-urchin, is irregu- 

 larly shaped and develops a tail. The tail is of no use 

 for swimming because it is not surrounded by water and 

 it is held fast by the sticky surface of the stigma ; but by 

 means of it the nucleus of the sperm cell reaches the egg 

 cell. The tail, or pollen tube, grows longer and longer 

 until it reaches down the style to the ovary ; the nucleus 

 of the cell then works its way down through the tube, 

 punctures and enters the egg cell and unites with the 

 nucleus which it finds there (Fig. 59). This is the 

 process of fertilization. The new cell, like the fertilized 



