Ill] 



THE BRACKEN FERN 



41 



indented apex. A succession of these is produced, 

 so that the possibility of carrying out their functions 

 may be spread over a considerable period. 



When mature their condition is such that on 

 access of external fluid water, as when rain falls, 

 both of these organs, if ripe, burst. Naturally the 

 lower surface of the prothallus on which they are 



Fig. 8. A. An antheridium of a Fern, mature and containing 

 numerous sperm -cells. C. A similar antheridium after rupture 

 and escape of the spermatozoids. B. A spermatozoid more 

 highly magnified, showing its spiral form during its movements 

 in water hy means of the numerous thread-like cilia. (From 

 F. Darwin's Elements of Botany.) 



borne will be moistened by any shower that wets 

 the soil thoroughly, and the rupture of such as are 

 ripe ensues. The male organs discharge their contents 

 as spermatozoids into the water, in which they 

 are capable of moving their spirally curled bodies 

 rapidly by means of the active lashings of numerous 

 cilia (Fig. 8). The female organs under similar 



