SPEEMATOPHYTES : GYMNOSPEEMS 



187 



This " awakening " of the seed is spoken of as its " ger- 

 mination,'' but this must not be confused with the germi- 

 nation of a spore, which is real germination. In the case 

 of the seed an oospore has germinated and formed an embryo, 

 which stops growing for a time, and then resumes it. This 

 resumption of growth is not germination, but is what 



Fig. 157. Tip of pollen tube of Cycas revoluta, containing the two spiral, malticiliate 

 sperms. — ^After Ikeno. 



happens when a seed is said to " germinate." This second 

 period of development is known as the extra-seminal, for it 

 is inaugurated by the escape of the sporophyte from the 

 seed (Fig. 154). 



104. The great groups of Gymnosperms. — There are at 

 least four living groups of Gymnosperms, and two or three 



