GLOSSARY OF BOTANICAL TERMS 169 



FERTILIZATION. 



Plants are fertilized by pollen falling upon 

 the stigma of the pistil or carpel. 



Pollen grains are cells containing fertiliz- 

 ing matter. When highly magnified they are 

 seen to be of various shapes. When pollen 

 grains adhere to the sticky surface of the 

 stigma, or are caught in its hairy surface, they 

 emit long root-like tubes full of fertilizing mat- 

 ter. These are pushed down through the style 

 to the ovary and the seed-eggs are thus ferti- 

 lized and developed into seeds. The ovary and 

 its seeds gradually enlarge, and when the lat- 

 ter are ripe they are ejected in various ways to 

 start life upon their own account. 



Examples of Pollen grains emitting tubes, 

 showing tubes descending. (Both greatly 

 magnified.) (77, A and B) 



Pollen is sometimes collected into sticky 

 masses, as in Orchids. 



METHODS OF FERTILIZATION. 

 Self -Fertilization. A flower is said to be 

 self-fertilized when its seed-eggs are fertilized 

 by pollen from its own anthers. (78) 



