CLASSES. 2O9 



distinguish from one another the three classes into 

 which Spermaphytes are divided. 



i. Are there any yew trees in your neighbourhood ? 

 They are dioecious, you know (p. 123), -and I want you 

 to fmd some of the pistil bearing trees. They will be 

 in flower in April, but later in the season will be all 

 the better for you. Then you will see the little green 

 seeds, each with its greenish cup in which it is fixed 

 something like an egg in art egg cup. Gradually the 

 greenish cup thickens and becomes juicy and red. 

 It is called an " arillus" (Fig. 174). You have 

 often seen them, I dare say, and very pretty they are. 



But what I want you to notice is not the cup 

 or arillus, but the seed which it partly surrounds. 

 I want you to remember that it is a seed, and not like 

 the acorn or nut, a seed enclosed in an ovary. 

 For instance, if you pick some common flower of good 

 size, primrose or poppy or hyacinth, one of which the 

 corolla has faded away, one which has " gone to seed." 

 Where is the seed ? Quite right. It is ripening 

 within the ovary ; cut open the ovary and there you 

 can see the seed. You can see the seed of the yew 

 quite well without cutting or disturbing anything. 

 The ovules of the yew were not enclosed in ovaries, 

 and when they were fertilized (p. 133), ripened as 

 uncovered or naked seeds. So plants of this habit 

 are called gymnosperms* because their seeds are 



* See note * on next page. 

 15 



