210 t . FLOWER-LAND. 



uncovered and naked ; whilst plants like the primrose 

 are called angiosperms* because their seeds are 

 enclosed within an ovary. 



This is one of the characteristic differences which 

 you should remember, so that you may be ab^e to 

 distinguish from one another the "classes" into which 

 spermaphytes have been divided. 



2. The next difference is also connected with the 

 seed. It has to do with the number of the coty- 

 ledons of the embryo, about which I have already 

 told you (p. 154). And you know that when the 

 embryo of the seed has only one cotyledon (p. 176) 

 the plant is 'called a monocotyledon ; when it has 

 two opposite cotyledons the plant is called a dicotyle- 

 don. But when the seed has more than two cotyle- 

 dons (some of the gymnosperms have as many as 

 fifteen) the plant is called a poly 'cotyledon. 



So far then we have the three classes of Phseno- 

 gams arranged as follows : 



Class I. Angiosperms and Dicotyledons. 

 Class II. Angiosperms and Monocotyledons. . t 

 Class III. Gymnosperms and Dicotyledons or 

 Polycotyledons. 



But these differences are not always easy for you to 

 see. So I will mention some other differences which 

 you can observe more easily. 



*From the Greek " aggos" " aggcion," a vessel,, or "gumnos" 

 naked, and " sperma" seed. 



