106 REPRODUCTION 



female cell is formed deep in the tissues of the sporophyte, 

 a delicate motile sperm cell could not reach the egg. 

 Hence the small spore in germinating produces a tube 

 that penetrates the tissues and allows the sperms to pass 

 down through it. Sperms of ferns and mosses have cilia, 

 and are active in motion. The sperms of seed plants 

 evidently have no need for activity of motion, yet we find 

 that the sperms of some of the lower seed plants have 

 cilia, which strongly suggests that their ancestors had 

 need for ciliated and actively moving sperms. 



