206 



PRACTICAL BOTANY. 



sions is the production of true seeds, which are the result 

 of the fertilization of the embryo cell by the receipt of 

 the contents of the pollen cell. The embryo cell is borne 

 in a pistil, and the pistil or pistils of a flower are known 

 as the gyncecium ; the stamens with their pollen-bearing 

 anthers constitute the androecium. According as the 

 embryo cells or ovules are exposed to the direct action of 

 the pollen grains, or are borne in closed ovaries, the Sper- 

 maphytes are divided into two classes : 



CLASS I. THE GYMNOSPERMS. 

 CLASS II. THE ANGIOSPERMS. 



CLASS I. The Gymnosperms. In these the ovules are 

 borne on the lower part of the inner surface of modified 

 leaves which form a cone or female 

 flower ; the pollen is also borne on 

 modified leaves forming a small cone 

 or male flower. At the season of fer- 

 tilization the ovules are exposed to 

 the air, the pollen falls directly upon 

 them, and they are fertilized by the 

 passing of the contents of the pollen 

 grains into the ovules through tubes 

 which develop from the inner coat of 

 the pollen grains. The leaves of the 

 cone then close, remain closed during 

 the development, and open at matu- 

 rity to discharge the seed. The Gym- 

 nosperms include the Cycads, which 

 are native in hot climates ; the Coni- 

 fers, which include the Pines and re- 

 lated trees and which are native in 

 temperate and cold climates ; and the 

 Joint Firs, which are native in hot 

 climates. 



y 



r 



FIG. 132. A , apollen grain 

 of the Gymnosperm, 

 Ceratozamia longi- 

 folia, on the point of 

 beginning to develop ; 

 B, the same after the 

 tuhe has partially de- 

 veloped. (After Ju- 

 ranyi.) 



